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This BMR calculator estimates your basal metabolic rate — the calories your body burns at complete rest — using the Mifflin-St Jeor equation, plus your full daily burn at every activity level. Runs entirely in your browser.
How your BMR is calculated
Your basal metabolic rate is the energy your body spends doing nothing but staying alive — running your heart, brain, lungs, kidneys and the constant repair of cells. It is the biggest single chunk of your daily calorie burn, usually 60 to 70 percent of the total. This calculator uses the Mifflin-St Jeor equation, the formula dietitians consider the most reliable estimate from height, weight, age and sex. For men it is 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women the last term is − 161. The table then multiplies your BMR by an activity factor to show what you actually burn in a day at each lifestyle level.
BMR vs TDEE — which number do you use?
BMR is only the resting piece. The number you eat around is your TDEE — BMR times an activity factor — because it counts the calories you burn walking, training and digesting. Never set your intake at your BMR; that is below what your body needs even on a rest day. If you want the full picture with maintenance and weight-change targets in one place, use the TDEE Calculator, and to turn a target into protein, carbs and fat, use the Macro Calculator.
What changes your BMR
Bigger and younger bodies have higher BMRs, and men average higher than women of the same size because they carry more lean mass. The one factor you can influence is muscle: lean tissue is more metabolically active than fat, so strength training slowly raises your resting burn. Aggressive crash diets push the other way — sustained very-low-calorie intake signals the body to conserve energy and can suppress BMR, which is a big reason gentle, sustainable deficits outperform extreme ones.
Frequently Asked Questions
What is BMR (basal metabolic rate)?
What is the difference between BMR and TDEE?
Which BMR formula does this calculator use?
Can I lower or raise my BMR?
Sources
- Mifflin, M. D., St Jeor, S. T., et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 51(2), 241–247.
- Harris, J. A., & Benedict, F. G. (1919). A Biometric Study of Basal Metabolism in Man.
- Katch, F., & McArdle, W. — lean-body-mass equation.