BMR Calculator

Estimate the calories your body uses at complete rest, by two well-known equations side by side.

For information only, not medical advice. BMR equations give estimates for healthy adults.

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The equations use sex at birth, because it changes the typical share of muscle.

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Your BMR

The energy you use doing nothing

Even lying perfectly still, your body is busy. Your heart beats, your lungs work, your brain runs and your cells repair themselves. The energy all of that takes is your basal metabolic rate, or BMR, and for most people it is the biggest single part of the calories they use each day.

This basal metabolic rate calculator estimates your BMR with the Mifflin-St Jeor equation and shows the revised Harris-Benedict result next to it, so you can see how much the two well-known formulas agree for you.

How to use it

  1. Choose metric or US units.
  2. Pick your sex, then fill in your age, height and weight.
  3. Read your BMR by Mifflin-St Jeor, then the Harris-Benedict figure and the gap between them.
  4. To turn BMR into daily calories with activity, carry on to the TDEE calculator.

The BMR formulas

Mifflin-St Jeor (men) = 10 × kg + 6.25 × cm − 5 × age + 5
Mifflin-St Jeor (women) = 10 × kg + 6.25 × cm − 5 × age − 161
Harris-Benedict, revised (men) = 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age
Harris-Benedict, revised (women) = 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age

The Harris-Benedict equation dates from 1919 and was revised by Roza and Shizgal in 1984. The Mifflin-St Jeor equation followed in 1990, built from resting energy measured in 498 healthy adults aged 19 to 78; its authors reported that Harris-Benedict overestimated by about 5%. That is why Mifflin-St Jeor is the main figure here.

Worked example

A 35 year old woman is 165 cm tall and weighs 68 kg.

  • Mifflin-St Jeor: 10 × 68 + 6.25 × 165 − 5 × 35 − 161 = 1,375.25, about 1,375 calories
  • Revised Harris-Benedict: 447.593 + 9.247 × 68 + 3.098 × 165 − 4.330 × 35 = 1,436 calories
  • The gap: about 61 calories

Her BMR is about 1,375 calories a day by Mifflin-St Jeor, or about 57 calories an hour. Harris-Benedict comes out 61 calories higher, which fits the pattern its critics described.

BMR, RMR and TDEE

Three terms that are easy to mix up
TermMeaning
BMR, basal metabolic rateEnergy used at complete rest, measured under strict conditions
RMR, resting metabolic rateEnergy used at rest in everyday conditions; usually a little higher than BMR
TDEE, total daily energy expenditureBMR plus digestion plus all activity: the calories you use in a whole day

In everyday use, BMR and RMR are often treated as the same thing, and the equations here are sometimes described as estimating either one.

Making sense of your BMR

  • Do not eat only your BMR to lose weight. It covers rest alone; real daily needs are higher.
  • Muscle matters. Two people of the same weight can have different BMRs if one carries more muscle.
  • BMR falls a little with age and with weight loss, so recalculate after a big change.
  • Equations estimate; only a lab test measures. Most people land within a couple of hundred calories of the estimate, but some are further off.

Frequently asked questions

What is basal metabolic rate?

Basal metabolic rate, or BMR, is the number of calories your body needs at complete rest to keep breathing, circulating blood, controlling temperature and running your organs. It is usually the largest part of the calories you use in a day. Activity and digestion add the rest.

What is the Harris-Benedict equation?

It is one of the oldest equations for estimating BMR, first published in 1919 and revised in 1984. It uses weight, height, age and sex. Later research found it tends to overestimate a little, so this calculator shows it next to the Mifflin-St Jeor result rather than instead of it.

Is BMR the same as RMR?

Not quite. BMR is measured under strict conditions: fasted, fully rested, at a comfortable temperature. RMR, resting metabolic rate, is measured in more relaxed conditions and comes out slightly higher. For everyday planning the difference is small, and the two terms are often used for the same figure.

Should I eat my BMR to lose weight?

No. Your BMR only covers complete rest, so eating just that much leaves nothing for daily movement and can be too low. A gentler approach is to eat a little below your total daily needs. The calorie calculator shows targets that never go under 1,000 calories a day.

Related calculators

  • TDEE CalculatorTotal daily energy expenditure for your activity level, with every level side by side.
  • Calorie CalculatorDaily calories to keep your weight steady, with gentle targets to lose or gain.
  • BMI CalculatorBody mass index for adults, the CDC weight category, and the healthy weight range for your height.
  • Calorie Deficit CalculatorA daily calorie target below maintenance, never under 1,000, and your weight lost as a percentage.
  • Body Fat CalculatorBody fat percentage from a tape measure (US Navy method), with a BMI based estimate.

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