BMR Calculator
Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure to understand how many calories your body needs each day.
What is BMR?
Your Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, and cell production while at complete rest. It represents the minimum energy your body requires to stay alive.
Your Total Daily Energy Expenditure (TDEE) adds the calories burned through daily activities and exercise on top of your BMR, giving you the total calories you need each day to maintain your current weight.
About the Formulas
Mifflin-St Jeor
Developed by Mifflin et al. (1990), this equation estimates resting energy expenditure from weight, height, age and sex. Individual needs can differ from the prediction.
Harris-Benedict
Originally published in 1919 by James Arthur Harris and Francis Gano Benedict, later revised by Roza and Shizgal in 1984. One of the oldest and most well-known BMR equations, though it tends to slightly overestimate calorie needs compared to more modern formulas.
Katch-McArdle
Uses estimated lean body mass rather than total weight alone. Its result depends on the body-fat estimate you enter; uncertainty in that input carries through to the calorie estimate.
Separate energy used at rest from energy used across a whole day. This tool estimates both resting needs and activity-adjusted expenditure; neither is a direct measurement of your metabolism.
From resting calories to estimated daily needs
Worked example: a resting estimate of 1,600 kcal/day multiplied by each activity factor. The same factors appear in the simple calculator.
| Activity setting | Multiplier | Estimated TDEE (kcal/day) |
|---|---|---|
| Sedentary | 1.2 | 1,920 |
| Lightly active | 1.375 | 2,200 |
| Moderately active | 1.55 | 2,480 |
| Very active | 1.725 | 2,760 |
| Extra active | 1.9 | 3,040 |
Choosing an equation
All three are predictive equations. Body composition and measurement quality affect their usefulness.
| Equation | Inputs | Interpretation |
|---|---|---|
| Mifflin–St Jeor | Weight, height, age, sex | Starting estimate of resting expenditure |
| Revised Harris–Benedict | Weight, height, age, sex | Alternative resting estimate |
| Katch–McArdle | Weight and body-fat estimate | Depends on estimated lean mass |
BMR, resting expenditure and TDEE
BMR describes basal energy use under controlled conditions. Equations commonly described as BMR calculators estimate resting expenditure. TDEE includes daily movement, exercise and other energy costs, so it is a different number.
A Mifflin–St Jeor worked example
The equation uses 10 × weight in kg + 6.25 × height in cm − 5 × age, then adds 5 for the male equation or subtracts 161 for the female equation. At 70 kg, 175 cm and age 30, this gives approximately 1,649 or 1,483 kcal/day respectively.
Avoid counting the same workout twice
Choose an activity setting that reflects a typical week. If the multiplier already includes exercise, adding all exercise calories again can overstate daily needs. Use the detailed mode thoughtfully and compare estimates with your longer-term observations.
Frequently asked questions
Is BMR my daily calorie target?
No. A resting estimate does not include the full energy cost of daily life. The activity-adjusted estimate answers a different question and still needs individual interpretation.
Why does my watch give a different result?
Devices and equations use different inputs and assumptions. Neither number is a direct measurement of your full daily expenditure. Compare trends consistently rather than expecting exact agreement.
Methods and references
Reference tables use the same calculations and benchmark values as the interactive tool.