BMR Calculator

BMR calculator at a glance#

Your basal metabolic rate (BMR) is the number of calories your body burns at rest to keep basic functions like breathing, circulation and cell repair going. This calculator uses the Mifflin-St Jeor formula, the method the page below describes as the most accurate, from your weight, height, age and sex.

The BMR formula is: men = 10 x weight in kg + 6.25 x height in cm minus 5 x age plus 5; women use the same formula but subtract 161 instead of adding 5. For a 30-year-old man who weighs 70 kg and is 175 cm tall: 700 + 1093.75 minus 150 + 5 = 1648.75, which rounds to 1649 calories per day at rest.

BMR is not the same as your total daily calorie burn. Your total daily energy expenditure (TDEE) is your BMR multiplied by an activity factor, from 1.2 if you are sedentary up to 1.9 if you are very active. So the 1,649 BMR above becomes about 1,979 calories per day for a sedentary day (1,649 x 1.2) and about 2,556 for a moderately active one (1,649 x 1.55).

Enter your weight, height, age and sex in the calculator above for your exact BMR and daily calorie estimate. These figures are estimates: muscle mass, genetics and health all shift the real number, so use the result as a starting point rather than an exact reading.

What BMR includes#

Your basal metabolic rate is the energy your body spends at complete rest to stay alive: pumping blood, breathing, keeping your temperature steady, and repairing cells. It is the largest part of most people's daily calorie burn, typically around 60 to 70 percent of the total. It does not include any movement, so any activity on top adds to it.

What changes your BMR#

A few factors move the number. Muscle burns more energy at rest than fat, so more lean mass raises BMR, which is why strength training nudges it up over time. BMR tends to fall with age as muscle declines, often from around 40 onward. Larger and taller bodies have a higher BMR because there is more tissue to maintain. Sex matters too, since men on average carry more muscle, which is why the formula adds 5 for men and subtracts 161 for women. Prolonged severe dieting can lower BMR as the body conserves energy.

BMR, RMR and TDEE#

These three overlap but are not the same. BMR is measured under strict resting conditions. Resting metabolic rate (RMR) is measured under less strict conditions and comes out slightly higher, so the terms are often used interchangeably. Total daily energy expenditure (TDEE) is the full picture: your BMR multiplied by an activity factor from 1.2 for sedentary up to 1.9 for very active. TDEE is the number you actually eat against to lose, maintain or gain weight. The answer block above shows a worked TDEE example.

Using BMR for weight goals#

Find your TDEE first, then set calories relative to it. To lose weight, eat below your TDEE; a deficit of about 500 calories a day is a common target for steady loss. To gain, eat above it. To maintain, match it. Recheck your BMR after a noticeable weight change, since it falls as you lose weight and the old number will overstate your needs.

An estimate, not an exact reading#

Formula-based BMR is an estimate. It works well for average body composition but is less accurate for very muscular or very high body-fat individuals, since it does not measure lean mass directly. The Katch-McArdle formula, which uses lean body mass, can fit those cases better. Use the result as a starting point and adjust based on how your weight actually responds over a few weeks.

Frequently asked questions#

What is basal metabolic rate?#

It is the minimum number of calories your body needs at complete rest to keep basic functions running, such as breathing, circulation and cell repair. It is your calorie burn before any movement is added.

How is BMR calculated?#

This calculator uses the Mifflin-St Jeor formula: men = 10 x weight in kg + 6.25 x height in cm minus 5 x age plus 5; women subtract 161 instead of adding 5. The Harris-Benedict and Katch-McArdle formulas are alternatives.

How accurate are the estimates?#

They are good estimates for typical body composition but can be off for people with much more or much less muscle than average, because the formula infers metabolism from weight, height, age and sex rather than measuring lean mass.

How many calories is a typical BMR?#

It varies with body size, but resting needs commonly fall around 1,200 to 1,800 calories a day for adult women and around 1,500 to 2,000 for adult men. Your exact figure depends on your weight, height, age and sex.

What raises BMR?#

More muscle from strength training, a larger body size, and, temporarily, pregnancy. Avoiding prolonged severe calorie deficits also helps, since extreme dieting signals the body to conserve energy.

How do I find my total daily calorie needs?#

Multiply your BMR by an activity factor: 1.2 sedentary, about 1.375 light activity, 1.55 moderate, 1.725 very active, 1.9 extremely active. That product is your TDEE, the calories you burn in a full day.

Does BMR change with age?#

Yes. It tends to decline from around age 40 as muscle mass decreases. Keeping up strength training and protein intake helps slow that drop.

How often should I recalculate?#

Recalculate after a weight change of roughly 10 pounds or more, or every few months, so your calorie target stays matched to your current body.