BMR Calculator

Your Basal Metabolic Rate — the calories your body burns at complete rest — compared across the three standard formulas.

Sex
yrs
Height
cm
Weight
kg
%

What is BMR?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — powering your heart, brain, liver and every other organ. It typically accounts for 60–70% of everything you burn in a day, which makes it the foundation of any calorie target. This BMR calculator compares the three standard equations side by side.

How it works

  • Mifflin–St Jeor (1990): 10 × weight + 6.25 × height − 5 × age (+5 men / −161 women). Rated the most accurate for healthy adults in the American Dietetic Association's systematic review — this is our headline number.
  • Harris–Benedict (1918, revised 1984): the classic equation, still widely used, though it tends to overestimate slightly.
  • Katch–McArdle: 370 + 21.6 × lean mass (kg). Shown if you enter your body fat percentage — the best choice for very lean or very muscular people, because it works from lean mass rather than total weight.

Frequently asked questions

Why is my BMR different from my smartwatch's number?

Wearables estimate resting burn with their own formulas and add movement on top. Differences of 100–200 kcal between methods are normal — pick one number, be consistent, and adjust based on real-world weight change.

Can I raise my BMR?

Meaningfully, only one way: carry more muscle. Each kilogram of muscle burns a little more at rest, and the training that builds it burns far more. Crash dieting does the opposite — it lowers BMR through weight loss and adaptation.

Should I eat below my BMR?

It's not dangerous by itself, but it's rarely necessary. Sensible fat-loss targets sit between BMR and TDEE. Very-low-calorie diets should only be done under medical supervision.

References

  1. Mifflin MD, St Jeor ST, et al. Am J Clin Nutr. 1990;51(2):241–247.
  2. Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370–373. Revised by Roza AM, Shizgal HM. Am J Clin Nutr. 1984;40(1):168–182.
  3. Frankenfield D, et al. J Am Diet Assoc. 2005;105(5):775–789.

Related

These results are estimates for healthy adults and are not medical advice. Consult a health professional before making major changes to your diet or training.

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