BMR Calculator

By Sofia Andersen · Last updated 15 October 2026

Lie still for a day, eat nothing, move nothing, and your body would still burn energy. Breathing. Keeping your heart beating. Holding your temperature. Running the quiet background work of being alive. That burn is your BMR. For most people it makes up well over half of everything they burn in a day. Everything else, walking, working, training, even digesting food, sits on top of it.

General information only, not medical advice. If weight, energy, or health is on your mind, talk with a qualified health professional. Urgent symptoms need urgent care, not a calculator.

What the number is for

Sex, age, height, and weight. That is all the formula needs. The result comes back in calories per day, alongside what that number becomes at a few activity levels. The calculator shows BMR first, then three activity presets beside it: sedentary, lightly active, and moderately active. A wider set, from very active to extra active, sits one tap further in. Switching presets is the fastest way to see how much daily movement changes the total.

Pick the activity level that matches an average week, not a holiday or a heroic one. If you train hard but sit the rest of the day, the lighter settings will probably fit better than you expect.

The formula, then a real day

This calculator uses the Mifflin-St Jeor equation (1990), the formula most dietitians reach for, because it held up well when researchers tested it against measured resting metabolism.

Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5

Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

Weight drives the biggest share, because a larger body costs more to run. Height adds a little. Age trims a little each year, mostly because muscle tends to shrink with age. The final +5 or −161 is the sex adjustment in the formula, reflecting average differences in body composition.

Take a 30-year-old man who weighs 80 kg and stands 180 cm tall. Start with weight: 10 × 80 = 800. Then height: 6.25 × 180 = 1,125. Then age: 5 × 30 = 150. Put it together: 800 + 1,125 − 150 + 5 = 1,780 calories a day. That is his BMR: what his body would use in a day of total rest.

Real days add movement. Multiply by an activity factor to get total daily energy, or TDEE. Sedentary (×1.2): 1,780 × 1.2 = 2,136 calories. Lightly active (×1.375): 1,780 × 1.375 = 2,447.5, which rounds to 2,448 calories. Moderately active (×1.55): 1,780 × 1.55 = 2,759 calories. Results round to the nearest whole calorie. Notice how much the total moves with activity: the same resting body burns about 600 calories more on a moderately active day than on a sedentary one.

Three letters people mix up

BMR is the strictest measure: at rest, in a lab, after fasting, in a comfortable room. It is the floor.

RMR, resting metabolic rate, is measured under looser conditions and usually lands a little higher than BMR, often by 10 percent or so. In everyday talk, people use the two interchangeably, and the difference rarely matters outside a lab.

TDEE is the whole day: BMR plus movement, work, training, and digestion. When someone asks how many calories they burn in a day, TDEE is the number they mean.

BMR alone cannot tell you how much to eat. It can tell you the floor under your intake. Many plans keep everyday eating at or above BMR and let the deficit come from the activity part of the day, not from under-eating the body’s resting needs. If you are considering eating below your BMR for any length of time, that is worth talking through with a clinician first.

If this wasn’t the one, the calorie calculator builds maintenance, deficit, and surplus numbers on top of BMR, and the BMI calculator adds the height-and-weight screening angle. The body fat percentage calculator estimates body fat from tape measurements, and the ideal weight calculator gives a healthy weight range by height. There is also a longer read, TDEE vs BMR, on what each number means and how they fit together. Or browse all health calculators and all calculators on CalcKits.

Frequently asked questions

What is BMR?

BMR is basal metabolic rate: the calories your body uses at complete rest to keep breathing, circulation, temperature, and basic cell repair going. It is the floor under your daily burn, before any movement.

How is BMR different from TDEE?

BMR is rest only. TDEE is the whole day: BMR times an activity factor, covering movement, work, exercise, and digestion. TDEE is the number that lines up with maintenance calories.

Can I raise my BMR?

Muscle is the main lever. Strength training and enough protein support muscle, which raises resting burn modestly. Age and height cannot be changed, and crash dieting tends to lower BMR by losing muscle along with fat.

One more time, plainly: this page is general information, not medical advice, a diagnosis, or treatment. It cannot replace a qualified health professional who knows your history. If symptoms worry you, or anything feels urgent, get urgent care rather than waiting on a calculator result.