BMR Calculator
Free BMR calculator: your basal metabolic rate by Mifflin–St Jeor, revised Harris–Benedict and Katch–McArdle, side by side. Runs in your browser.
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- ✓ Free, no limits
BMR is what you burn at complete rest — multiply by an activity factor (or use the calorie calculator) for daily needs. Estimates, not medical advice.
This BMR calculator estimates your basal metabolic rate — the calories your body burns per day at complete rest, just running its organs — by the three published formulas, side by side: Mifflin–St Jeor, the revised Harris–Benedict, and Katch–McArdle if you know your body-fat percentage.
Worked example: a 30-year-old man of 80 kg and 180 cm gets 1,780 kcal from Mifflin–St Jeor and about 1,854 from Harris–Benedict; at 15% body fat, Katch–McArdle reads about 1,839. The spread is the point: formulas that only see height and weight must guess your composition, while Katch–McArdle works from lean mass — which is why it is the pick for very muscular or very lean people.
BMR is not an eating target — you burn more than it the moment you stand up. Multiply by an activity factor, or use the calorie calculator, to get daily needs; eat at BMR level only under professional supervision. Like every formula, these describe the average person of your size, and real metabolisms scatter around that. Estimates, not medical advice; nothing you enter is uploaded.
Frequently asked questions
What is BMR?
Basal metabolic rate: the energy your body spends per day at complete rest — heart, brain, breathing, temperature. It is typically 60–70% of everything you burn; movement and digestion sit on top of it.
Which BMR formula is most accurate?
Mifflin–St Jeor is the best validated from height and weight alone, which is why dietitians default to it. If you genuinely know your body-fat percentage, Katch–McArdle is better still, because it works from lean mass directly.
Should I eat at my BMR to lose weight?
Generally no — BMR is below what you burn on any normal day, so eating at it is a steeper deficit than it looks. Take TDEE (BMR × activity) and subtract a moderate amount instead; the calorie calculator does exactly that.
Is my data uploaded?
No. All three formulas run in your browser; your measurements are never sent anywhere.