Three equations compared
Mifflin-St Jeor as the main result, with Harris-Benedict and Katch-McArdle to show the gap.
Health & wellness
BMR calculator
Adult basal metabolic rate from age, sex, height and weight, with a comparison of the main predictive equations.
Age and measurements
The result appears as soon as the fields are filled in. It remains a statistical estimate.
Sex used by the equation
Height
If you know it, the Katch-McArdle equation is added to the comparison.
Your estimated basal metabolic rate
Mifflin-St Jeor
kcal/day
-
Energy your body would use over 24 hours at complete rest, to breathe, circulate blood and keep its temperature.
By equation
- Mifflin-St JeorReference
- -
- Revised Harris-Benedict
- -
- Katch-McArdle
- -
Enter your body fat to add the Katch-McArdle equation, based on lean body mass.
Method & sources
The Mifflin-St Jeor equation, the most reliable of the common equations for adults, gives the main result. Revised Harris-Benedict and, when body fat is entered, Katch-McArdle are shown for comparison.
Formula
Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161 · Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5Limitations
- The equations provide an estimate and do not replace a measurement by indirect calorimetry.
- Body composition, health status, some medications and other individual factors can change actual expenditure.
- Katch-McArdle is no more accurate than the others if the body fat percentage entered is approximate.
Sources
- Mifflin et al. (1990) - predictive equation for resting energy expenditure
- Roza and Shizgal (1984) - revision of the Harris-Benedict equations
- McArdle, Katch and Katch - Exercise Physiology (Katch-McArdle equation)
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How does this tool work?
Your basal metabolic rate is the energy your body uses at complete rest over a day. This calculator estimates it with the Mifflin-St Jeor equation, compares it with Harris-Benedict and Katch-McArdle, and gives the result in kilocalories and kilojoules.
Choose the sex used by the equation, then enter your age, height and weight in metric, imperial or stones: the result appears as you type. Imperial measurements are converted to centimetres and kilograms before the calculation.
The main result comes from Mifflin-St Jeor. The other equations show how far two estimates can differ; if you know your body fat percentage, Katch-McArdle works out the rate from lean body mass.
How to use this tool
Enter your profile
Choose the sex used by the equation, then enter your age, height and weight in the unit you prefer.
Add body fat if you know it
This optional field adds the Katch-McArdle equation to the comparison.
Read the result
Keep the order of magnitude and the gap between equations in mind, then move on to the TDEE calculator to account for activity.
Good to know
Kilocalories and kilojoules
The result is given in both units, as on food labels.
Your choice of units
Centimetres and kilograms, feet and pounds, or stones: the result updates as you type.
The basal metabolic rate equations
Each equation estimates resting expenditure from simple measurements. Mifflin-St Jeor is the most widely used today.
Mifflin-St Jeor
Women: 10 × weight + 6.25 × height − 5 × age − 161 · Men: 10 × weight + 6.25 × height − 5 × age + 5
Revised Harris-Benedict
Women: 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age · Men: 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Katch-McArdle
370 + 21.6 × lean mass, where lean mass = weight × (1 − body fat ÷ 100)
- weight
- Weight in kilograms
- height
- Height in centimetres
- age
- Age in years
The equations provide an estimate and do not replace a measurement by indirect calorimetry.
Use cases
Know your resting expenditure
Get an order of magnitude of the energy your body uses over 24 hours without any activity.
Compare the equations
See how much Mifflin-St Jeor, Harris-Benedict and Katch-McArdle differ for your profile.
Prepare your calorie needs
The basal metabolic rate is the starting point of daily expenditure, estimated next with an activity level.
Tips and best practices
- Use recent height and weight measurements to reduce input-related differences.
- Treat the basal metabolic rate as an order of magnitude: it is not your total energy expenditure over a day.
- Only enter body fat if it comes from a reliable measurement; a rough value makes Katch-McArdle less accurate than Mifflin-St Jeor.
Frequently asked questions
What does basal metabolic rate represent?
It is the energy the body uses over 24 hours at complete rest to maintain essential functions: breathing, circulation, temperature regulation and organ activity.
Which equation should I use?
Mifflin-St Jeor is the reference equation for most adults: it comes closest to measured values. Katch-McArdle can be more accurate for very muscular or very lean people, provided the body fat percentage is reliable.
Why don’t the equations give the same result?
They were built from different groups of people, at different times, and do not use the same variables. A gap of a few dozen kilocalories is normal and is a reminder that these are estimates.
Is BMR the same as my daily calorie needs?
No. It only covers resting expenditure. Total daily expenditure also includes physical activity and digestion; the TDEE calculator estimates it from your activity level.
What is the difference between kcal and kJ?
They are two units of energy: one kilocalorie equals 4.184 kilojoules. Food labels in many countries show both.
Can I use this calculator during pregnancy or under 18?
No. It is intended for adults and is not designed for pregnancy, growth or medical situations that require adapted reference values.
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