TDEE stands for Total Daily Energy Expenditure. It represents the total number of calories your body burns in 24 hours including baseline metabolism, daily movement, physical exercise, and food digestion.

How accurate are standard TDEE formulas?

Static formulas like Mifflin-St Jeor provide widely accepted baseline estimates for most adults. However, individual variations in non-exercise activity (NEAT) and metabolic adaptation mean that formula results are estimates, not exact medical measurements. Using a real-world calibration tool tracking intake vs. weight can provide highly personalized precision.

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BMR Calculator: Calculate Your Basal Metabolic Rate

✍️ Written by: Dr. Michael Chen, PhD in Nutritional Sciences

🩺 Medically Reviewed by: Dr. Sarah Jenkins, MD, Board Certified Endocrinologist

📅 Last Updated: September 2026

You enter your age, height, weight, and sex into a BMR calculator and get a calorie number. But then the confusion starts. Is that number how many calories you should eat? Why does another calculator give you a different result? And does a higher or lower BMR mean your metabolism is better or worse?

These questions can make calorie planning harder than it needs to be. Our BMR Calculator gives you a clear starting estimate using the Mifflin-St Jeor equation and explains what the result means, how it is calculated, and where its limits are. The goal is not to present one number as a perfect measurement. It is to give you a transparent estimate that you can understand and use as part of a broader calorie-planning process.

What Is BMR?

BMR stands for Basal Metabolic Rate.

It describes the energy your body uses to support basic physiological functions while at rest under strict laboratory conditions. These functions include breathing, circulation, maintaining body temperature, supporting brain function, and normal cellular activity.

Your BMR does not represent all the energy you use during a normal day.

Walking, exercising, working, cooking, cleaning, and digesting food all require additional energy. This is why your total daily energy expenditure is generally higher than your BMR.

A simple way to understand the core distinction:

BMR = estimated resting energy expenditure (cellular baseline at 100% rest)
TDEE = estimated total daily energy expenditure (resting expenditure + movement + exercise + digestion)

Online calculators do not directly measure your BMR. They use prediction equations based on information such as age, sex, height, and weight.

Important: Your BMR result is an estimate of resting energy expenditure. It is not automatically the number of calories you should eat each day.

How Does the BMR Calculator Work?

Our BMR Calculator uses the Mifflin-St Jeor equation to estimate resting energy expenditure.

You enter:

Age
Sex
Height
Weight

The calculator applies the equation to these values and returns an estimated number of calories per day.

The original Mifflin-St Jeor research developed predictive equations for resting energy expenditure using data from 498 healthy adults. Their resting energy expenditure was measured using indirect calorimetry. (PubMed [1])

Technically, the Mifflin-St Jeor equation estimates resting energy expenditure (REE). Consumer calculators commonly use the result as a BMR estimate because BMR and resting metabolic rate are closely related concepts.

Calculation Method Overview

Primary Equation: Mifflin-St Jeor (1990 clinical standard)
Required Inputs: Age, biological sex, height, and body weight
Output Result: Estimated resting energy expenditure (REE) in calories/day
Important Limitation: The result is a population-based prediction, not a direct laboratory measurement of your personal metabolism.

Research comparing prediction equations with indirect calorimetry shows that Mifflin-St Jeor can be useful, but prediction errors still occur at the individual level. (PubMed [2])

How to Use the BMR Calculator

Using the calculator requires only a few basic details.

Step 1: Enter Your Age

Enter your age in years. Age is one of the primary independent variables used by the Mifflin-St Jeor equation, as baseline metabolic expenditure tends to change predictably across adulthood.

Step 2: Select Your Sex

Select the option that matches the equation you want the calculator to use. The Mifflin-St Jeor equation applies different baseline constants for biological men and women due to average differences in lean mass distribution. (PubMed [1])

Step 3: Enter Your Height

Enter your height using the available unit options (Centimeters or Feet & Inches). Height reflects body surface area and structural organ scale.

Step 4: Enter Your Weight

Enter your current body weight in Kilograms or Pounds. Body mass is the single strongest driver of total resting metabolic output.

Step 5: Calculate Your BMR

The calculator applies the selected equation and gives you an estimated resting calorie expenditure. Remember that this number is a starting estimate, not a direct measurement of your metabolism.

What Does Your BMR Result Mean?

Your BMR result estimates how much energy your body may use at rest based on the equation and the information you entered. It does not tell you exactly how many calories you should eat.

Term	Definition & Practical Meaning
BMR	Estimated energy expenditure at complete physiological rest under strict fasting/post-absorptive conditions.
RMR / REE	Resting metabolic or energy expenditure measured or estimated under less strict conditions than laboratory BMR.
TDEE	Estimated total energy expenditure across 24 hours including resting expenditure, movement, exercise, and digestion.
Maintenance Calories	An estimated daily calorie intake associated with maintaining stable body weight over time.
Calorie Deficit	A daily calorie intake below estimated total daily energy expenditure, required for fat loss.
Calorie Surplus	A daily calorie intake above estimated total daily energy expenditure, required for mass/muscle gain.

For example, if your estimated BMR is 1,500 calories per day, that does not mean 1,500 calories is your daily calorie requirement. Your total energy expenditure is higher because you move, walk, exercise, digest food, and perform other routine daily activities.

How to Calculate BMR

The Mifflin-St Jeor equation is widely used to estimate resting energy expenditure. It utilizes four main body parameters: Weight, Height, Age, and Sex.

Mifflin-St Jeor Equation Breakdown

For Men: BMR estimate = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

For Women: BMR estimate = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

These equations are simplified versions of the predictive equations published in the original Mifflin-St Jeor study. (PubMed [1])

Because the original research describes these as resting energy expenditure equations, it is more precise to call the calculator result an estimated resting energy expenditure even though consumer calculators commonly label it BMR.

BMR Calculation Worked Example

Suppose a 30-year-old woman weighs 65 kg and is 165 cm tall.

Applying the female Mifflin-St Jeor formula step-by-step:

Step 1 (Weight): 10 × 65 kg = 650

Step 2 (Height): 6.25 × 165 cm = 1,031.25

Step 3 (Age penalty): 5 × 30 years = 150

Step 4 (Female Constant): -161

BMR Estimate = 650 + 1,031.25 − 150 − 161 = 1,370.25 kcal/day

The estimated resting energy expenditure is therefore about 1,370 calories per day.

This does not mean she should automatically eat 1,370 calories per day. Her actual daily energy needs depend on activity and other components of energy expenditure.

Other BMR Formulas

Mifflin-St Jeor is not the only equation used to estimate resting energy expenditure. Other commonly encountered formulas include the Revised Harris-Benedict equation and Katch-McArdle equation. Different formulas can produce different results because they were developed using different sample populations and variables.

Revised Harris-Benedict Equation

The original Harris-Benedict equation was developed in 1919 and revised in 1984. It uses variables such as age, sex, height, and weight. Different versions of the Harris-Benedict equation exist, so the exact formula matters when comparing results.

Katch-McArdle Formula

The Katch-McArdle approach uses lean body mass rather than biological sex as a direct variable.

Katch-McArdle Equation: RDEE = 370 + (21.6 × Lean Body Mass in kg)

Because the formula depends on lean body mass, its result also depends on the accuracy of your body-composition estimate. Home bioelectrical impedance scales and calipers can produce imperfect body-fat estimates, so the result should still be treated as an estimate.

BMR vs RMR

BMR and RMR stand for:

BMR: Basal Metabolic Rate
RMR: Resting Metabolic Rate

The terms are closely related but are not technically identical. BMR has stricter laboratory measurement conditions (measured immediately upon waking after 8 hours of sleep and a 12-hour overnight fast in a temperature-controlled room). RMR is measured under less restrictive resting conditions and is often used as a practical estimate of resting energy expenditure. In consumer health and fitness content, BMR, RMR, and REE are sometimes used interchangeably. For a calculator, the important point is that these values describe resting energy expenditure rather than your complete daily calorie expenditure. (Healthline [3])

BMR vs TDEE

BMR and TDEE describe different parts of your overall energy expenditure energy balance.

BMR estimates energy used at 100% rest.
TDEE estimates your total energy expenditure across the entire day.

TDEE includes resting energy expenditure, physical activity, structured exercise, non-exercise daily movement (NEAT), and the thermic effect of food (TEF). This means your TDEE is generally higher than your BMR.

Physiological Pipeline Model:

BMR → Daily Movement & Physical Activity → Thermic Effect of Food → TDEE

If you want to estimate your daily calorie needs, calculating BMR alone is not enough.

How BMR Is Used to Estimate TDEE

A common practical approach in clinical dietetics is to multiply estimated resting energy expenditure by an activity factor:

Estimated TDEE = BMR × Activity Factor

Activity Level Category	Example Factor	Typical Routine Description
Sedentary	1.200	Little to no regular exercise, desk-bound job
Lightly Active	1.375	Light exercise 1–3 days/week or light daily movement
Moderately Active	1.550	Moderate exercise 3–5 days/week and active routine
Very Active	1.725	Hard exercise 6–7 days/week or active physical job
Extra Active	1.900	Very heavy physical job combined with daily intense training

These factors are estimation tools. They are not direct measurements of how many calories you burn. For example, if your estimated BMR is 1,500 calories and you use an activity factor of 1.55:

Estimated TDEE = 1,500 × 1.55 = 2,325 calories/day

This gives you a starting estimate of total daily energy expenditure. For a more detailed calculation, use our homepage TDEE Calculator.

How to Choose Your Activity Level

Choosing the right activity level can be difficult because people often overestimate or underestimate their daily movement. Consider your normal routine over a full typical week rather than one unusually active day.

Sedentary

You spend most of the day sitting at a desk or driving, and perform little to no structured exercise.

Lightly Active

You have a desk job but walk regularly or perform 1 to 3 light exercise sessions per week.

Moderately Active

You exercise 3 to 5 times per week and maintain an active daily schedule (e.g. 8,000–10,000 daily steps).

Very Active

You perform frequent or intense workout sessions 6 to 7 days per week and have a physically active lifestyle.

Extra Active

You have an intensely demanding physical job (construction, farming, athletics) combined with rigorous daily training.

Activity factors are approximate. If your calculated TDEE does not match your real-world weight trend over time, that does not necessarily mean the calculator is wrong. It may mean that your actual activity or energy expenditure differs from the general estimate.

What Factors Affect BMR?

There is no single BMR that applies to everyone. Several physiological factors directly affect resting energy expenditure:

Body Size

Larger bodies generally require more total energy to support their organ systems and metabolic processes at rest.

Height

Height is included in the Mifflin-St Jeor equation and several other prediction equations to account for body surface area.

Age

Age is another variable used by common resting-energy equations. Resting energy expenditure tends to decline gradually across adulthood, primarily due to changes in muscle mass and endocrine regulation.

Sex

Mifflin-St Jeor uses different baseline constants for biological men and women to account for average population differences in fat-free mass.

Body Composition

Lean body mass (muscle, organ, bone tissue) is an important factor in resting energy expenditure. Two people can have identical body weight but different body compositions and therefore different resting energy needs. The original Mifflin-St Jeor research found fat-free mass to be a strong predictor of resting energy expenditure. (PubMed [1])

Individual Biological Differences

Prediction equations cannot capture every biological difference between individuals, such as thyroid hormone levels, genetics, or mitochondrial efficiency. This is one reason why a BMR calculator should be treated as an estimate rather than an exact measurement.

Why Does BMR Matter?

BMR gives you a useful starting point for understanding your energy needs. It helps explain why your total daily calorie needs are higher than the calories your body uses at rest. It can also be used as one part of a broader calorie-planning process:

Calorie Planning Flow: BMR → TDEE → Calorie Target

This is far more practical and healthy than treating your resting BMR as your daily calorie ceiling.

What Is a Good BMR?

There is no single "good" BMR. A BMR estimate of 1,300 calories is not automatically better or worse than an estimate of 1,700 calories. Your estimated resting energy expenditure depends on height, weight, age, sex, and body composition. Comparing your BMR with another person's BMR can therefore be misleading. A higher BMR does not automatically mean better health, and a lower BMR does not automatically mean something is wrong.

What Is a Normal BMR by Age?

There is no single normal BMR value for each age group. Two people of the same age can have very different BMR estimates because their height, weight, sex, and body composition may differ. For this reason, an age-only BMR chart cannot accurately tell you what your personal BMR should be.

How to Use BMR for Weight Loss

BMR can help you understand your baseline energy needs, but it should not be used alone to set a weight-loss calorie target. A practical process involves three steps:

Estimate BMR: Calculate your baseline resting energy expenditure.
Estimate TDEE: Account for daily movement, step counts, and workouts.
Set a Suitable Calorie Target: Subtract a moderate percentage (e.g. 15%–25%) from TDEE.

The key rule to remember: BMR is not your weight-loss calorie target. Your calorie needs depend on your complete daily energy expenditure and individual goals.

Should You Eat Your BMR to Lose Weight?

There is no general rule that says you should eat exactly your BMR. BMR estimates resting energy expenditure. It does not represent your complete daily calorie needs. Eating at or near BMR for extended periods without medical supervision can cause fatigue, nutritional deficiencies, and extreme hunger. For individualized nutrition advice, consult a qualified healthcare professional or registered dietitian.

Can You Increase BMR?

Be careful with claims that a specific food, supplement, or exercise can dramatically increase BMR. There is no simple method that guarantees a massive surge in resting energy expenditure for everyone. Lean body mass is associated with resting energy expenditure, so increasing your muscle mass through resistance training can support higher resting energy needs over time. Regular exercise also increases overall daily energy expenditure, but increasing your workout calories (EEE) is not the same as directly altering your baseline BMR. A better goal is to support overall health, strength, physical activity, and healthy body composition rather than chase a specific BMR number.

How Accurate Is a BMR Calculator?

A BMR calculator can provide a useful baseline estimate, but it cannot tell you your exact metabolic rate. The Mifflin-St Jeor equation was developed from measured resting energy expenditure in 498 healthy adults. Later validation research found that it can be a useful prediction equation, while also showing that prediction accuracy varies between individuals and populations. (PubMed [1])

Accuracy can vary because:

Your actual resting energy expenditure may differ from population averages.
Your body composition (muscle-to-fat ratio) may differ from sample populations.
Input measurements (height, weight) may contain slight inaccuracies.
Different mathematical equations yield slightly different estimates.
Measurement conditions and stress levels affect resting expenditure.

A calculator should therefore present its result as an estimate rather than an exact measurement.

Why Do BMR Calculators Give Different Results?

Different calculators may use different underlying equations. One may use Mifflin-St Jeor, while another may use Harris-Benedict or Katch-McArdle. Different input assumptions, rounding rules, and body-composition algorithms can also produce different results. A difference between two calculators does not mean one is broken; compare the methodology before deciding why the numbers differ.

Can BMR Be Measured?

Yes. Resting energy expenditure can be measured rather than estimated. One established clinical method is indirect calorimetry. Indirect calorimetry measures oxygen consumption (VO2) and carbon dioxide production (VCO2) to calculate real-time metabolic heat production. This is fundamentally different from an online calculator. An online calculator uses a prediction equation based on statistical averages, whereas indirect calorimetry measures your actual physiological data under controlled laboratory conditions. Research shows that prediction equations can have meaningful individual errors compared with measured resting energy expenditure. (PubMed [2])

Why Does BMR Change When You Lose Weight?

Your estimated BMR changes as your body mass changes. For example, if your weight decreases by 10 kg, entering your new weight into the same equation will produce a lower estimated resting energy expenditure. This does not automatically mean that your metabolism is "damaged." It simply reflects the physical reality that a smaller body requires fewer calories to support its tissues at rest. For this reason, calorie targets should be periodically reassessed as your body weight changes instead of treating one initial BMR number as permanent.

Special Populations and BMR Calculators

Standard BMR equations are designed as general prediction tools for healthy adults and may not be appropriate for every situation. Extra caution is needed for:

Children and growing adolescents
Pregnant or breastfeeding women
Individuals with thyroid disorders or metabolic conditions
Clinical nutrition or medical recovery situations
Elite athletes with extreme lean body mass percentages

Research has found that prediction accuracy can vary across populations and individual characteristics. (PubMed [4]) If you need individualized calorie or nutrition guidance, speak with a qualified healthcare professional.

Common BMR Calculation Mistakes

Using BMR as Your Daily Calorie Target: BMR only estimates resting burn, not total daily needs.
Confusing BMR With TDEE: TDEE includes activity, movement, and food digestion.
Comparing Your BMR With Someone Else's: Different body sizes and compositions yield different baseline numbers.
Treating the Calculator as an Exact Measurement: Prediction equations provide statistical estimates, not laboratory data.
Entering Incorrect Information: Minor errors in height, weight, or age distort formula outputs.
Assuming Every Formula Gives the Same Result: Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle apply different variables.
Believing One BMR Number Defines Your Metabolism: Human metabolism is dynamic and responds to lifestyle, sleep, and training.

BMR and Macros

BMR alone is not enough to determine your complete macronutrient needs. Macronutrients refer to Protein, Carbohydrates, and Fat. Your macro targets depend on your total calorie intake, activity level, fitness goals, and preferences. A logical planning sequence is:

BMR → TDEE → Calorie Target → Macro Distribution

This keeps resting energy expenditure separate from total daily calorie needs. You can calculate customized protein, carb, and fat targets with our Macro Calculator.

Frequently Asked Questions

What is BMR?

BMR stands for Basal Metabolic Rate. It describes the energy your body uses under strict resting conditions to support basic physiological functions like breathing and circulation. Online calculators estimate it using predictive equations.

How do I calculate my BMR?

A common clinical method is the Mifflin-St Jeor equation, which uses age, sex, height, and body weight to estimate resting energy expenditure.

What is the difference between BMR and TDEE?

BMR estimates energy expenditure at rest. TDEE estimates your total energy expenditure across 24 hours, including daily movement, exercise, and food digestion.

Do I burn calories while sleeping?

Yes. Your body continues burning calories during sleep to power baseline physiological functions such as respiration, brain activity, and tissue repair.

What is a good BMR for my age?

There is no single "good" BMR for an age group. Your BMR depends on height, weight, sex, and body composition. A higher or lower number simply reflects body size and tissue mass.

Should I eat my BMR to lose weight?

Not as a general rule. BMR represents resting energy expenditure, not your total energy intake requirement. Weight loss targets should be calculated based on TDEE and individual health needs.

How accurate is a BMR calculator?

A BMR calculator provides a statistical estimate, not a direct measurement. Accuracy varies by individual. Laboratory indirect calorimetry provides direct physiological measurement.

Why is my BMR different from another calculator?

Calculators may use different underlying formulas (Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle), rounding methods, or unit inputs. Check the methodology of each tool.

Should my BMR go down when I lose weight?

Yes, your estimated BMR will naturally decrease as body weight decreases because smaller body mass requires less energy to maintain at rest.

Related Calculators and Guides

Once you know your estimated BMR, continue your calorie planning with our dedicated suite of tools:

TDEE Calculator — Estimate your total daily energy expenditure based on BMR and activity level.
Maintenance Calorie Calculator — Find your exact zero-gain calorie target.
Calorie Deficit Calculator — Calculate optimal calorie targets and timelines for fat loss.
Macro Calculator — Customize your daily protein, carb, and fat distributions.
Methodology & Scientific References — Explore our mathematical engine and clinical studies.

Sources & Scientific References

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. (PubMed [1])
Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789. (PubMed [2])
Healthline Editorial Team. Basal Metabolic Rate Calculator & Overview. (Healthline [3])
Weijs PJ. Validity of predictive equations for resting energy expenditure in US and European overweight and obese adults. Public Health Nutr. 2008;11(1):85-94. (PubMed [4])
Sabounchi NS, et al. Predicting resting energy expenditure: a critical appraisal and validation review. Int J Obes. 2023. (PubMed [5])

A Word From Our Team

When developing a BMR calculator, the goal should not be to simply display a single calorie number. A useful tool must explain how that number was estimated, what the calculation represents biologically, and why the result can differ from a measured metabolic rate. That is why our calculator uses a documented equation and clearly separates estimated resting energy expenditure from total daily calorie needs.

Your BMR is a useful starting point, but it is only one part of your overall energy expenditure. Your physical activity, daily movement, body composition, food intake, and sleep quality also matter. Once you understand your estimated BMR, you can use our TDEE Calculator to estimate your total daily energy expenditure and continue your calorie-planning process. For personalized health or nutrition guidance, calculator estimates should always be considered alongside advice from a qualified healthcare professional.

Important: This calculator is intended for informational and educational purposes. It does not diagnose medical conditions or provide individualized medical or nutrition treatment.

← Back to Main TDEE Calculator

Day	Daily Calories Eaten	Morning Weight
Click "Fill 14-Day Sample Data" above to test adaptive expenditure calibration instantly!

TDEE Calculator: Calculate Your Total Daily Energy Expenditure

You enter your age, weight, height, and activity level into a TDEE calculator and get a calorie number. But what does that number actually mean? If another calculator gives you a different result, it can be hard to know which number to trust. The problem is that a TDEE estimate is not a direct measurement of how many calories your body burns each day.

This calculator is designed to make the number easier to understand. It uses the Mifflin-St Jeor equation to estimate resting energy expenditure and an activity factor to estimate total daily energy expenditure. It also explains how the result is calculated, how to choose your activity level, why estimates can differ, and how to compare the estimate with your real-world results. The Mifflin-St Jeor equation was developed from measured resting energy expenditure in 498 healthy adults. (PubMed [1])

What Is TDEE?

TDEE stands for Total Daily Energy Expenditure.

It is an estimate of the total energy, expressed in kilocalories (kcal), that your body expends over a 24-hour period to support baseline survival, daily movement, physical work, and food digestion.

Your daily energy expenditure includes energy used at rest, physical activity, and the thermic effect of food. Resting energy expenditure is generally the largest component for most people, accounting for 60% to 75% of total daily burn. (NCBI [2])

Your individual energy needs are affected by factors such as:

Age: Metabolic rate gradually declines with age, largely due to loss of muscle mass (sarcopenia) and hormonal shifts.
Body size: Larger bodies with greater mass require more energy to move and maintain cellular functions.
Body composition: Muscle tissue consumes roughly 13 kcal/kg daily at rest compared to fat's 4.5 kcal/kg.
Physical activity: Workouts, cardio, and sports elevate total energy expenditure above baseline.
Daily movement: Unplanned movement like walking, standing, and fidgeting significantly alters daily burn.
Food intake: Digesting, absorbing, and processing food requires metabolic energy.
Physiological factors: Thyroid hormones, body temperature regulation, and genetics impact metabolic rate.

This means two people with similar height and weight can still have different actual energy needs based on muscle mass and step counts.

A TDEE calculator uses an equation and activity assumptions to estimate your needs. It does not directly measure your metabolism.

Why Your TDEE Matters

Your estimated TDEE gives you a starting point for understanding your daily calorie needs.

If you want to maintain your weight, the estimate can help you choose a starting maintenance calorie target.

If you want to lose weight, it can help you understand how a calorie deficit relates to your estimated energy expenditure.

If you want to gain weight, it can help you plan around a calorie surplus.

The important part is how you use the number.

Your calculated TDEE should be treated as a starting estimate, not an exact measurement. Your body-weight trend and calorie intake over time can provide useful information about whether the estimate matches your actual needs.

The Three Components of Daily Energy Expenditure

Total daily energy expenditure has three main components.

Resting Energy Expenditure

Resting energy expenditure, or REE, is the energy your body uses to support normal functions while at rest.

This includes essential processes such as breathing, circulation, brain activity, liver function, and kidney filtration.

Internal organs account for most REE: liver (~27%), brain (~19%), skeletal muscle (~18%), kidneys (~10%), and heart (~7%). REE is usually the largest part of total daily energy expenditure. (NCBI [2])

Physical Activity

Physical activity increases your energy use above resting levels and is split into exercise and non-exercise movement.

Exercise energy expenditure includes planned workouts such as:

Walking for exercise
Running
Cycling
Strength training
Swimming
Sports

It also includes everyday movement (NEAT) such as walking around your home, working, shopping, and physical tasks.

Non-exercise activity can vary widely between people, which is one reason calorie needs are difficult to predict with a simple formula. (NCBI [3])

Thermic Effect of Food

Your body also uses energy to digest, absorb, and process food.

This is called the thermic effect of food, or TEF (roughly 10% of daily intake).

Protein has the highest thermic effect (20%–30%), carbs moderate (5%–10%), and fats lowest (0%–3%).

Together, resting energy expenditure, physical activity, and the thermic effect of food make up total daily energy expenditure. (NCBI [2])

How TDEE Is Calculated

A standard TDEE calculator usually uses two main steps.

Step 1: Estimate your resting energy expenditure.

Step 2: Apply an activity factor.

A common estimation method is:

Estimated TDEE = Estimated Resting Energy Expenditure × Activity Factor

Many consumer calculators call the first number BMR, or Basal Metabolic Rate.

Strictly speaking, BMR and REE are different measurements. BMR has more specific testing conditions, while REE is commonly used in practical prediction equations. In everyday calculator use, the terms are often treated as interchangeable because the difference is usually relatively small. (NCBI [4])

The Mifflin-St Jeor Equation

The Mifflin-St Jeor equation is a widely used predictive equation for estimating resting energy expenditure.

The original study was published in 1990 and developed the equation using data from 498 healthy adults measured with indirect calorimetry. (PubMed [1])

For Men

REE = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

For Women

REE = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

These equations produce an estimate.

They do not directly measure how much energy your body uses.

Research has found that Mifflin-St Jeor performs well among commonly used prediction equations, but no prediction equation is exact for every person or population.

Step 2: Apply Your Activity Factor

After estimating resting energy expenditure, the calculator applies an activity factor.

A commonly used set of factors is:

Activity Level	Factor	General Description
Sedentary	1.2	Mostly sitting with little structured exercise (<5,000 steps/day)
Lightly Active	1.375	Light exercise 1–3 days/week or regular light movement (5,000–8,000 steps)
Moderately Active	1.55	Regular moderate exercise 3–5 days/week (8,000–11,000 steps)
Very Active	1.725	Frequent hard exercise 6–7 days/week (11,000–15,000 steps)
Extra Active	1.9	Very high activity or demanding physical labor work (>15,000 steps)

These factors are practical estimation categories.

They are not laboratory measurements.

Your daily activity can fall between categories, so focus on your normal routine rather than your most active week.

How to Choose Your Activity Level

Choosing an activity level is one of the most difficult parts of using a TDEE calculator.

Do not look only at your workouts.

Think about your complete day.

Ask yourself:

How much do I walk?
Do I sit for most of the day?
How often do I exercise?
How hard are my workouts?
How long do my workouts last?
Is my job physically demanding?
How active am I outside the gym?

For example, someone who trains three times per week but sits at a desk for most of the day may have a different total activity level from someone who trains three times per week and also walks or works on their feet for several hours.

Use the activity level that best represents your normal week, not your best week.

Worked TDEE Example

Consider a 28-year-old woman who weighs 65 kg, is 165 cm tall, and is moderately active.

First, estimate resting energy expenditure:

REE = (10 × 65) + (6.25 × 165) − (5 × 28) − 161

REE = 650 + 1,031.25 − 140 − 161

REE = 1,380.25 calories/day

Now apply the moderate activity factor of 1.55:

TDEE = 1,380.25 × 1.55

TDEE ≈ 2,139 calories/day

Her estimated TDEE would therefore be about 2,140 calories per day.

This is an estimate based on the information entered. It should not be interpreted as a precise measurement of her actual daily energy expenditure.

How to Use Your TDEE for Weight Maintenance

If your goal is to maintain your current weight, your estimated TDEE can be used as a starting point for your daily calorie intake.

For example, if your estimated TDEE is 2,400 calories, you could use 2,400 calories as an initial maintenance estimate.

Then monitor your weight trend over time.

If your average weight stays relatively stable, your actual maintenance intake may be close to the estimate.

If your weight consistently changes, your actual maintenance needs may differ from the calculated value.

This is why maintenance calories are better viewed as a real-world outcome rather than a number guaranteed by a calculator.

How to Use Your TDEE for Weight Loss

Weight loss generally requires a sustained energy deficit.

A calorie deficit means that energy intake is lower than energy expenditure over time.

Your estimated TDEE can provide a starting point for understanding your maintenance needs and choosing a calorie target.

For example:

Estimated TDEE = 2,400 calories/day

Moderate Deficit Target (-20%): 1,920 calories/day

A person trying to lose weight may choose a calorie intake below that estimate.

The appropriate calorie target depends on the individual and should not be based on the assumption that a larger deficit is always better.

Monitor your progress over time instead of judging the result from a single day.

How to Use Your TDEE for Weight Gain

Weight gain generally requires a sustained energy surplus over time.

If your estimated TDEE is 2,400 calories, eating more than your maintenance needs (e.g. 2,650 calories) may create a calorie surplus for muscle building.

Your target should be appropriate for your goal and circumstances.

As your body weight and activity change, your estimated calorie needs can change as well.

Understanding Your TDEE Calculator Results

Your calculator may show several numbers.

Each one has a different purpose.

Estimated Resting Energy Expenditure

This is the estimated energy your body uses at rest.

Many consumer calculators label this value as BMR even when the underlying equation estimates REE.

TDEE

TDEE is your estimated total daily energy expenditure.

It accounts for your estimated resting energy needs and the activity factor selected in the calculator.

Maintenance Calories

Maintenance calories describe an intake level associated with maintaining body weight over time.

Your estimated TDEE can be used as a starting estimate for maintenance calories.

It is not a guarantee that eating exactly that number will keep your weight unchanged.

Macronutrients

Macronutrients are nutrients your body needs in relatively large amounts.

The three main macronutrients are:

Protein (4 kcal/g)
Carbohydrates (4 kcal/g)
Fat (9 kcal/g)

A TDEE calculator can use your calorie target as the starting point for estimating a macro plan.

Macro targets are also estimates and should be selected according to the person's goals and dietary needs.

TDEE vs BMR

TDEE and BMR are related but different.

BMR / REE	TDEE
Focuses on energy used at rest	Estimates total daily energy expenditure
Does not include your complete daily activity	Accounts for activity through the calculation method
Used as the starting point in many TDEE calculations	Used to estimate daily calorie needs

A simple way to remember the difference:

BMR/REE = estimated energy needed at rest

TDEE = estimated energy used across the day

For scientific precision, BMR and REE are not exactly the same measurement. Consumer calculators often use the terms interchangeably. (NCBI [4])

TDEE vs Maintenance Calories

These terms are closely related, but they are not identical.

TDEE is an estimate of energy expenditure.

Maintenance calories describe an intake level associated with maintaining body weight over time.

A TDEE calculator can therefore provide a starting estimate for maintenance calories.

Your actual maintenance intake is better judged by looking at your calorie intake and body-weight trend over time.

How Accurate Is a TDEE Calculator?

A TDEE calculator provides an estimate.

It does not directly measure your total daily energy expenditure.

Prediction equations can be useful, but individual results can differ from the predicted value.

Your actual energy needs can be affected by:

Body size
Body composition
Age
Physical activity
Non-exercise movement
Food intake
Physiological factors
Changes in body weight

The activity factor also introduces uncertainty because people with the same reported activity level can have different daily movement patterns.

For this reason, a calculator result should be treated as a starting estimate, not an exact calorie requirement.

Can TDEE Be Measured?

Yes, energy expenditure can be measured using scientific methods, but this is different from using an online calculator.

Resting energy expenditure can be measured using indirect calorimetry, which estimates energy expenditure from oxygen consumption and carbon dioxide production.

Total daily energy expenditure can also be studied using methods such as doubly labeled water.

An online TDEE calculator does not perform these measurements.

Instead, it estimates your energy needs from personal information, a prediction equation, and an activity assumption. (PubMed [5])

That difference is important.

A calculator estimates TDEE. It does not measure your actual TDEE.

Why Can Two TDEE Calculators Give Different Results?

You may enter the same information into two TDEE calculators and receive different results.

This can happen because calculators may use different:

Resting energy equations
Activity factors
Input assumptions
Body-composition methods
Calculation methods
Rounding rules

For example, one calculator may use Mifflin-St Jeor while another may use a different equation.

Some calculators also provide multiple formulas and advanced metrics. Current competitor calculators offer different combinations of formulas, activity tools, body-composition inputs, and macro calculations. (TDEE Calculator [6])

Different results do not automatically mean that one calculator is broken.

Before comparing numbers, check the method behind each calculation.

How to Check Your Estimated TDEE With Real-World Data

Your calculated TDEE is a starting estimate.

Your real-world results can help you understand how close that estimate is to your personal needs.

A practical process is:

Calculate your estimated TDEE.
Choose a reasonable calorie target.
Track your calorie intake consistently.
Weigh yourself under similar conditions.
Look at the trend over several weeks.
Compare your average intake with your weight trend.
Adjust your estimate when your results consistently differ from your goal.

Do not judge your maintenance calories from one day of data.

Body weight can change from water, food volume, sodium, glycogen, and other short-term factors.

A longer trend provides more useful information.

What If My TDEE Seems Too High or Too Low?

If your calculated TDEE does not seem to match your real-world results, check the assumptions before changing everything.

Possible reasons include:

Incorrect height or weight
Incorrect age
An activity level that is too high
An activity level that is too low
Different daily movement than expected
Individual differences in energy expenditure
Changes in body weight
Inconsistent calorie tracking

Start by checking your inputs.

Then compare the estimate with your longer-term weight trend.

A calculator is not necessarily wrong because its result differs from your actual experience. Prediction equations estimate population patterns and cannot capture every individual difference.

Why Does TDEE Change Over Time?

Your estimated energy needs can change as your body and routine change.

Factors that can affect your estimate include:

Changes in body weight
Changes in physical activity
Changes in daily movement
Changes in body composition
Changes in lifestyle or work routine

For example, after losing a significant amount of weight, your estimated energy needs may be different because your body size has changed.

You do not need to recalculate TDEE every day.

Recalculate when there has been a meaningful change in your body weight, activity, or routine.

Common TDEE Calculation Mistakes

Choosing an Activity Level Based Only on Exercise

Your total activity includes more than gym sessions.

Consider your daily movement and work routine too.

Choosing Your Most Active Week

Use your normal routine.

Do not select an activity level based on an unusually active week.

Treating TDEE as an Exact Number

TDEE calculators use prediction equations and assumptions.

The result is an estimate.

Using One Day of Weight Change

Daily weight can change for many reasons.

Use a longer trend instead.

Changing Several Variables at Once

If you change calories, exercise, activity level, and other habits at the same time, it becomes harder to understand what caused a change in your results.

Make changes carefully and monitor the trend.

Assuming a Larger Calorie Deficit Is Always Better

A larger deficit is not automatically a better approach.

Calorie targets should account for individual needs, goals, and circumstances.

How TDEE Relates to Macros

TDEE gives you an estimated calorie budget.

Macros divide calories among protein, carbohydrates, and fat.

For example, two diets can contain the same total calories while having different amounts of protein, carbohydrates, and fat.

Your TDEE therefore answers one question:

How much energy might I need each day?

A macro plan addresses another:

How might those calories be divided among macronutrients?

Macro targets are estimates too. They should be appropriate for your goals, dietary preferences, and individual needs.

Frequently Asked Questions

What does TDEE stand for? ▼

TDEE stands for Total Daily Energy Expenditure. It is an estimate of the total energy your body uses during a 24-hour period.

What is a TDEE calculator? ▼

A TDEE calculator estimates your daily energy expenditure using information such as age, sex, height, weight, and activity level.

How is TDEE calculated? ▼

A common method estimates resting energy expenditure and then multiplies it by an activity factor.

Estimated TDEE = Estimated REE × Activity Factor

What formula does this TDEE calculator use? ▼

The calculator uses the Mifflin-St Jeor equation to estimate resting energy expenditure and then applies an activity factor. The original Mifflin-St Jeor study was published in 1990. (PubMed [1])

Is Mifflin-St Jeor accurate? ▼

Mifflin-St Jeor is a widely used predictive equation and has performed well compared with several older equations. However, it is still a prediction and cannot be exact for every individual.

Is TDEE the same as maintenance calories? ▼

Not exactly.

TDEE is an estimate of energy expenditure. Maintenance calories describe an intake level associated with maintaining body weight over time.

TDEE can be used as a starting estimate for maintenance calories.

How accurate is a TDEE calculator? ▼

A TDEE calculator provides an estimate rather than a direct measurement.

Your actual energy needs can differ because activity, body composition, daily movement, and other factors vary between people.

Why do two TDEE calculators give different results? ▼

They may use different equations, activity factors, assumptions, or calculation methods.

Which activity level should I choose? ▼

Choose the level that best represents your normal overall activity, including exercise, work, walking, and other daily movement.

Can I use TDEE for weight loss? ▼

Yes. Your estimated TDEE can provide a starting point for understanding your maintenance calories and planning a calorie deficit.

Can I use TDEE for weight gain? ▼

Yes. Your estimated TDEE can provide a starting point for planning a calorie surplus.

Does TDEE change when I lose weight? ▼

It can. Changes in body weight and activity can change estimated energy needs.

Should I recalculate TDEE every day? ▼

No. Daily recalculation is usually unnecessary. Recalculate when your body weight, activity, or routine changes meaningfully.

Can TDEE be measured? ▼

Yes, energy expenditure can be measured using scientific methods such as indirect calorimetry and doubly labeled water. A normal online TDEE calculator estimates rather than measures your TDEE. (PubMed [5])

Should men and women calculate TDEE differently? ▼

The Mifflin-St Jeor equation uses different constants for men and women, so sex is one of its inputs. (PubMed [1])

What if my calculated TDEE seems too high or too low? ▼

Check your input information and activity level first. Then compare the estimate with your calorie intake and body-weight trend over several weeks.

Related Calculators and Guides

Use related tools and guides to understand different parts of your calorie and energy needs.

Calculators

TDEE Guides

These pages should be connected with relevant internal links so users can move naturally from calculation → understanding → planning → related tools.

Disclaimer

This TDEE calculator provides an estimate for general informational and educational purposes.

It does not directly measure your metabolism or total daily energy expenditure.

Individual calorie and energy needs vary.

This calculator is intended for general adult use. It is not a substitute for individualized medical or nutrition advice.

If you are pregnant or breastfeeding, have a medical condition, have a history of an eating disorder, take medication that affects appetite or body weight, or have specific nutrition concerns, speak with an appropriate healthcare professional before making major changes to your diet or calorie intake.

About This Calculator

This calculator uses a transparent calculation method so you can understand where your estimate comes from.

The calculation uses the Mifflin-St Jeor equation to estimate resting energy expenditure and an activity factor to estimate total daily energy expenditure. The original Mifflin-St Jeor research measured resting energy expenditure using indirect calorimetry in 498 healthy adults. (PubMed [1])

The result is an estimate, not a laboratory measurement. The goal is to give you a useful starting point while making the calculation, assumptions, and limitations clear.

Important publishing note: For strong E-E-A-T, add a real author/reviewer name, credentials only if genuine, “last reviewed/updated” date, methodology/source links, and a clear About page. Don't add invented personal fitness or nutrition experience. The article itself now establishes expertise through transparent methodology, scientific sourcing, limitations, and practical interpretation rather than fabricated first-person claims. (PubMed [1])

BMR Calculator: Calculate Your Basal Metabolic Rate

What Is BMR?

How Does the BMR Calculator Work?

Calculation Method Overview

How to Use the BMR Calculator

Step 1: Enter Your Age

Step 2: Select Your Sex

Step 3: Enter Your Height

Step 4: Enter Your Weight

Step 5: Calculate Your BMR

What Does Your BMR Result Mean?

How to Calculate BMR

Mifflin-St Jeor Equation Breakdown

BMR Calculation Worked Example

Other BMR Formulas

Revised Harris-Benedict Equation

Katch-McArdle Formula

BMR vs RMR

BMR vs TDEE

How BMR Is Used to Estimate TDEE

How to Choose Your Activity Level

Sedentary

Lightly Active

Moderately Active

Very Active

Extra Active

What Factors Affect BMR?

Body Size

Height

Age

Sex

Body Composition

Individual Biological Differences

Why Does BMR Matter?

What Is a Good BMR?

What Is a Normal BMR by Age?

How to Use BMR for Weight Loss

Should You Eat Your BMR to Lose Weight?

Can You Increase BMR?

How Accurate Is a BMR Calculator?

Why Do BMR Calculators Give Different Results?

Can BMR Be Measured?

Why Does BMR Change When You Lose Weight?

Special Populations and BMR Calculators

Common BMR Calculation Mistakes

BMR and Macros

Frequently Asked Questions

What is BMR?

How do I calculate my BMR?

What is the difference between BMR and TDEE?

Do I burn calories while sleeping?

What is a good BMR for my age?

Should I eat my BMR to lose weight?

How accurate is a BMR calculator?

Why is my BMR different from another calculator?

Should my BMR go down when I lose weight?

Related Calculators and Guides

Sources & Scientific References

A Word From Our Team

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Unsure Which Activity Level You Are?

Step 1: What is your average daily step count?

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What Is TDEE?

Why Your TDEE Matters

The Three Components of Daily Energy Expenditure

Resting Energy Expenditure

Physical Activity

Thermic Effect of Food

How TDEE Is Calculated

The Mifflin-St Jeor Equation

For Men

For Women

Step 2: Apply Your Activity Factor

How to Choose Your Activity Level

Worked TDEE Example