BMR calculator

Estimate how many calories your body uses at complete rest. Mifflin–St Jeor is shown first, with two other well-known formulas next to it.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Add your activity level to get daily calories burned with the TDEE calculator.

The formulas

W is weight in kg, H is height in cm and A is age in years. Results are in kilocalories (kcal, the "calories" on food labels) per day.

Mifflin–St Jeor (1990): 10W + 6.25H − 5A + 5 (men) or − 161 (women)
Revised Harris–Benedict (Roza & Shizgal 1984):
men 88.362 + 13.397W + 4.799H − 5.677A
women 447.593 + 9.247W + 3.098H − 4.330A
Katch–McArdle: 370 + 21.6 × lean body mass (kg), where lean mass = W × (1 − body fat %)

Worked example

A 30-year-old man, 180 cm and 80 kg:

Mifflin–St Jeor: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal
Harris–Benedict: 88.362 + 1,071.76 + 863.82 − 170.31 = 1,853.6 kcal
Katch–McArdle at 20% body fat: 370 + 21.6 × 64 = 1,752.4 kcal

Which one to use

A 2005 systematic review by the Academy of Nutrition and Dietetics (then the American Dietetic Association) found that Mifflin–St Jeor predicted resting rate within 10% of measured values more often than the other equations it tested. That's why it's the default here. Katch–McArdle can suit lean, muscular people if you know your body fat percentage.

Limitations

Even the best formula can be off by 10% or more for an individual.
The formulas are for adults. They don't apply during pregnancy or breastfeeding, or with conditions or medicines that change metabolism.
BMR isn't what you burn in a day. Multiply by an activity factor for that, as the TDEE calculator does.

For anyone under 18, these calculators show a pointer to the CDC's BMI-for-age calculator and growth charts instead of adult results, because children and teens are still growing.

Sources

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247.
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 1984;40:168–182.
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;105:775–789.
McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Lippincott Williams & Wilkins (Katch–McArdle equation).

Learn: BMR, RMR and TDEE explained · How many calories should I eat a day?

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

Man, 30, 180 cm, 80 kg: Mifflin–St Jeor 1,780 kcal ✓
Same man: revised Harris–Benedict 1,854 kcal ✓
Same man at 20% body fat: Katch–McArdle 1,752 kcal ✓
Woman, 40, 5 ft 5 in, 150 lb: Mifflin–St Jeor 1,351 kcal ✓
Age 16: adult formulas not used ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

What is a normal BMR?

It depends on size, age and sex. For example, Mifflin–St Jeor gives about 1,350 kcal for a 40-year-old woman who is 5 ft 5 in and 150 lb, and 1,780 kcal for a 30-year-old man who is 180 cm and 80 kg.

What's the difference between BMR and RMR?

BMR is measured under strict conditions after fasting and sleep. RMR is less strict and runs slightly higher. The formulas here estimate resting needs and are often used for either.

Why do the formulas give different numbers?

They were built from different groups of people. A difference of 50 to 100 kcal is normal.

Should I eat my BMR?

BMR is only what you'd burn lying still. Daily needs are higher. Use the calorie calculator for a daily figure.

Related calculators

TDEE calculatorTotal daily energy expenditure at every activity level.Calorie calculatorDaily calories to maintain, lose or gain weight at a steady rate.Body fat calculatorBody fat % from a tape measure (U.S. Navy method), with the ACE chart.Lean body mass calculatorLean body mass from height and weight (Boer, James and Hume).