BMR Calculator

Estimate your basal metabolic rate, the calories your body burns at complete rest, with the Mifflin-St Jeor and Harris-Benedict equations.

  • Reviewed October 2026
  • Formula and worked example below
  • Free, no sign-up, runs in your browser
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What is BMR?

Your basal metabolic rate is the energy your body needs to stay alive at rest: breathing, pumping blood, maintaining body temperature and repairing cells. For most people it accounts for 60–70% of all the calories they burn in a day.

The Mifflin-St Jeor equation

Published in 1990, the Mifflin-St Jeor equation is considered the most accurate everyday formula for healthy adults and is recommended by the Academy of Nutrition and Dietetics.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

A 30-year-old man who weighs 75 kg and is 175 cm tall: 750 + 1,093.75 − 150 + 5 = 1,699 kcal a day.

The calculator also shows the revised Harris-Benedict equation (1984) for comparison. It usually comes out 5–10% higher.

What raises or lowers BMR

  • Muscle mass. Muscle burns more energy at rest than fat, which is one reason strength training helps with weight management.
  • Age. BMR tends to fall slowly with age, mostly because of muscle loss.
  • Body size. Larger bodies need more energy to maintain.
  • Hormones and health. Thyroid conditions, some medications and pregnancy can change metabolic rate significantly.

BMR is not how much you should eat. To find your daily calorie needs, multiply BMR by an activity factor using the calorie calculator.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy you burn at complete rest. TDEE (total daily energy expenditure) adds the energy used for digestion, daily movement and exercise.

Which BMR formula is most accurate?

For healthy adults, the Mifflin-St Jeor equation is usually within about 10% of measured values and is the most widely recommended. The Katch-McArdle formula can be better if you know your lean body mass.

Should I eat my BMR in calories?

Usually not. Eating below BMR for long periods can lead to muscle loss and fatigue. Base calorie targets on TDEE instead.

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Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.