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BMR Calculator

Your basal metabolic rate — the calories your body burns at complete rest — computed with the two most used equations.

Fill in all fields to see your basal metabolic rate.

What is BMR?

Basal metabolic rate is the energy your body spends just staying alive: keeping your heart beating, lungs breathing, brain thinking, and cells repairing. Even if you spent an entire day in bed, you would still burn your BMR. For most people it is the single largest share of daily energy expenditure — typically 60 to 70 percent — which is why two people can eat identically, train identically, and still get different results.

BMR rises with body size and lean mass and falls slowly with age, roughly one to two percent per decade after your twenties. That decline is not destiny: much of it tracks the gradual loss of muscle, which strength training largely prevents.

The two equations

This calculator shows both widely used estimates. Mifflin-St Jeor, published in 1990, is the modern standard and the more accurate for today's population. Harris-Benedict dates to 1919 (revised 1984) and typically lands a little higher; it is included because many older plans and articles reference it. If the two disagree, trust Mifflin-St Jeor.

Mifflin-St Jeor

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (men) / − 161 (women)

From BMR to a calorie target

BMR alone is not the number to eat. To plan intake you need total daily energy expenditure — BMR multiplied by an activity factor between 1.2 and 1.9. The calorie calculator does that step and adds targets for losing or gaining; the macro calculator then splits the result into protein, carbs, and fat.

A practical way to use your BMR: think of it as your floor. Diets that push intake below it tend to backfire — energy drops, training quality falls, and lean mass goes with it. Sustainable fat loss happens in the space between BMR and TDEE.

Limits of the estimate

Formulas estimate from height, weight, age, and sex — they cannot see body composition. A muscular person is underestimated; someone with low lean mass is overestimated. Thyroid conditions, some medications, and aggressive dieting history shift the real number too. As with any estimate, the fix is feedback: track intake and weight for a few weeks in ActiveDay and let the trend tell you whether the number was right.

Frequently asked questions

  • What is a normal BMR?

    Most adults fall between roughly 1,200 and 2,000 kcal per day. Larger, younger, taller, and more muscular bodies burn more at rest; BMR also runs higher in men than women on average because of differences in lean mass.

  • Which BMR formula is most accurate?

    Mifflin-St Jeor is the best validated for healthy adults and is the one to use by default. Harris-Benedict tends to estimate slightly higher; if you know your body fat percentage, the Katch-McArdle formula based on lean mass can be more precise for lean individuals.

  • Can I increase my BMR?

    The main lever you control is muscle mass — each kilogram of muscle adds a small amount of resting burn, and strength training plus adequate protein builds it. Crash dieting works the other way: very low intakes cause the body to adapt downward.

  • Should I eat below my BMR to lose weight?

    Generally no. Your calorie deficit should come out of your TDEE, which includes activity, not out of your resting requirement. Eating below BMR is aggressive, hard to sustain, and usually unnecessary.

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