BMR Calculator: Calories Your Body Burns at Rest

Your basal metabolic rate (BMR) is the energy your body needs just to stay alive: breathing, circulation and keeping organs working. Enter your age, sex, height and weight to estimate it.

FreeNo sign-upRuns in your browserUpdated 2 Nov 2026
The formula uses different constants for each.
years
cm
kg
Your resultLive

Educational estimate only. It is not medical advice or a diagnosis. Talk to a doctor or registered dietitian before changing your diet or exercise.

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How to use this calculator

  1. Choose your sex.
  2. Enter your age in years.
  3. Enter height in cm and weight in kg.
  4. Read your BMR. It updates as you type.

The formula

Mifflin-St Jeor: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. The revised Harris-Benedict equation is shown for comparison.

Worked example

A 30-year-old man, 175 cm, 75 kg: 10 × 75 = 750, plus 6.25 × 175 = 1,093.75, minus 5 × 30 = 150, plus 5. BMR = 1,698.75, shown as about 1,699 kcal a day. Harris-Benedict gives about 1,763.

Understanding your result

BMR is not what you eat in a day. It is the floor, before movement, work and exercise. To estimate total daily needs, multiply by an activity factor, which the TDEE calculator does. Two people with the same numbers can still differ by a few hundred calories.

When to use it

  • Find the starting point for a calorie plan.
  • Understand why very low intakes are hard to sustain.
  • Compare how age or weight changes your resting needs.

Assumptions and limits

Educational estimate, not medical advice. A doctor or registered dietitian can give guidance that fits your health. The result is an estimate for adults. It does not account for muscle mass, thyroid conditions, medicines or pregnancy.

Frequently asked questions

What is the difference between BMR and RMR?

RMR is measured under looser conditions and is usually slightly higher. Calculators often use the two terms loosely.

Which formula is most accurate?

Mifflin-St Jeor is widely considered the most reliable of the common equations for most adults.

Should I eat my BMR in calories?

BMR is not a target. Total daily energy includes activity, so use the TDEE calculator.

Why does BMR fall with age?

People tend to lose muscle with age, and muscle burns more energy than fat.

Does muscle change BMR?

Yes. More lean mass raises resting energy use, which these formulas do not measure.