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BMR Calculator

Calculate your Basal Metabolic Rate using Mifflin-St Jeor, Revised Harris-Benedict, or Katch-McArdle formulas. See TDEE for all activity levels.

What is BMR Calculator?

The BMR Calculator estimates your Basal Metabolic Rate — the number of calories your body burns at complete rest just to sustain basic functions like breathing, circulation, and cell repair. BMR is the foundation for calculating total daily calorie needs at any activity level. This calculator supports three formulas: Mifflin-St Jeor (best for most adults), Revised Harris-Benedict, and Katch-McArdle (best for lean individuals who know their body fat percentage).

How to use

  1. 1 Select your biological sex.
  2. 2 Choose Metric or Imperial units.
  3. 3 Enter your age, height, and weight.
  4. 4 Select the BMR formula. Choose Katch-McArdle if you know your body fat % — it is more accurate for lean and athletic individuals.
  5. 5 Review your BMR and the TDEE estimates for all six activity levels.

Formula

Mifflin-St Jeor (male): BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5. Revised Harris-Benedict (male): BMR = 13.397×weight + 4.799×height − 5.677×age + 88.362. Katch-McArdle: BMR = 370 + 21.6×LBM(kg), where LBM = weight × (1 − body fat%).

Example calculation

A 28-year-old woman, 165 cm, 65 kg: Mifflin BMR ≈ 1,459 kcal/day. At moderate activity (×1.55) her TDEE is about 2,261 kcal. With Katch-McArdle at 25% body fat (LBM = 48.75 kg): BMR ≈ 1,423 kcal.

Frequently asked questions

What does BMR measure?

BMR is the minimum energy your body needs to stay alive at complete rest — digesting nothing, moving nothing, at neutral temperature. It accounts for roughly 60–75% of total daily energy expenditure for most people.

Which BMR formula is most accurate?

Mifflin-St Jeor is the most validated formula for the general adult population. Harris-Benedict tends to overestimate slightly. Katch-McArdle is the most accurate for lean athletes because it uses lean body mass and bypasses the confounding effect of excess fat on total weight.

How is BMR different from TDEE?

BMR is your resting calorie burn. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for movement, exercise, and the thermic effect of food. You always burn more than your BMR in daily life.

Does BMR decrease with age?

Yes. BMR declines roughly 1–2% per decade after age 20, partly because muscle mass decreases. Regular resistance training helps preserve muscle and keep BMR higher over time.

Can I eat exactly my BMR calories?

No. Your body burns more than BMR through all daily activity and digestion. Eating at BMR level creates a significant deficit and is unsafe outside of medical supervision.