Basal metabolic rate (BMR): what it is and how to calculate it
October 12, 2026 · 3 min read
Basal metabolic rate (BMR) is the number of calories your body burns at complete rest, just to keep your heart beating, your lungs working and your cells alive. For most adults it is between 1,200 and 2,000 calories a day and makes up about 60–70 percent of everything you burn.
How to calculate BMR
The Mifflin-St Jeor equation is the most accurate of the common formulas for most people:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Example: a 30-year-old man, 180 cm (5'11"), 80 kg (176 lb): (10 × 80) + (6.25 × 180) − (5 × 30) + 5 = about 1,780 calories.
BMR examples
| Profile | BMR |
|---|---|
| Woman, 25, 160 cm, 55 kg | about 1,265 kcal |
| Woman, 30, 165 cm, 65 kg | about 1,370 kcal |
| Woman, 45, 165 cm, 75 kg | about 1,395 kcal |
| Man, 25, 175 cm, 70 kg | about 1,675 kcal |
| Man, 30, 180 cm, 80 kg | about 1,780 kcal |
| Man, 45, 180 cm, 95 kg | about 1,855 kcal |
BMR is not the number you eat
BMR covers lying still all day. You also burn calories digesting food, moving around and exercising. Together that is your total daily energy expenditure (TDEE), which you get by multiplying BMR by an activity factor between 1.2 (sedentary) and 1.9 (very active).
For the man in the example with a moderately active week: 1,780 × 1.55 = about 2,760 calories. That is his maintenance level, and a weight-loss target is set from there, not from BMR. The full method is in how many calories should I eat a day.
What changes your BMR
- Body size. A bigger body burns more at rest. This is why BMR falls as you lose weight.
- Muscle mass. Muscle burns roughly 13 calories per kg per day at rest, fat about 4.5. The gap is real but smaller than fitness marketing suggests.
- Age. BMR drifts down with age, mostly because people lose muscle and move less.
- Sex. Men average higher because they carry more muscle at the same weight.
- Genetics and hormones. Two people with identical measurements can differ by a couple of hundred calories. Thyroid conditions shift BMR noticeably.
Can you raise your BMR?
Only a little. Strength training that adds or keeps muscle helps, and so does eating enough protein while losing weight. Green tea, spicy food and "metabolism boosters" have effects too small to matter. Moving more during the day changes your total burn far more than any change in BMR; see how many calories 10,000 steps burns.
Should you eat below your BMR?
As a general rule, no. A target under your BMR is an aggressive deficit that is hard to sustain and raises the risk of muscle loss and fatigue. A deficit of 300–500 calories below your TDEE is a safer starting point; the calorie deficit guide covers the numbers. People with medical conditions should set targets with a doctor or dietitian.
How accurate is the formula?
Mifflin-St Jeor lands within about 10 percent of measured values for most people. It is less accurate for very muscular people and those with a lot of excess weight. Treat the number as a starting point, track your intake and weight for two or three weeks, and adjust.
Let the app do the maths
Cal Crew asks for your height, weight, age, sex and activity on first launch and works out your daily calorie and macro targets from them. After that the job is logging meals, and a photo of your plate is enough for that.