Basal Metabolic Rate
BMR Calculator
Your basal metabolic rate is the calories your body burns at complete rest. This calculator estimates it with the Mifflin-St Jeor equation, then adds your activity to show your full daily burn too.
What is BMR?
Basal metabolic rate (BMR) is the energy your body uses just to keep you alive at rest — breathing, circulating blood, running your organs. It is the largest single part of your daily calorie burn, usually 60–70% of it, before you move at all. Strictly, the equation estimates your resting metabolic rate (measured under less strict conditions, so it reads slightly higher than true BMR), but like most tools it reports it as your BMR — the difference, explained.
How is BMR calculated?
BMR is calculated with the Mifflin-St Jeor equation: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5 for men, and the same with −161 for women. This calculator applies it to your inputs and shows the working. There is more on the maths in the equation explained.
| Weight | Men (180 cm) | Women (165 cm) |
|---|---|---|
| 60 kg | 1,580 kcal | 1,320 kcal |
| 70 kg | 1,680 kcal | 1,420 kcal |
| 80 kg | 1,780 kcal | 1,520 kcal |
| 90 kg | 1,880 kcal | 1,620 kcal |
| 100 kg | 1,980 kcal | 1,720 kcal |
What changes your BMR?
The biggest single driver of differences in BMR between people is lean (fat-free) mass — muscle and organs burn far more at rest than fat. In one study of 150 adults, fat-free mass alone accounted for about 63% of the variation in BMR, more than any other factor. Beyond that, BMR is affected by fat mass, age (it drifts down over the years) and thyroid hormone levels. Larger bodies have higher BMRs mainly because they carry more lean tissue, and men average higher than women largely because of body-composition differences rather than sex itself.
BMR, TDEE and your calorie target
BMR on its own is not your daily calorie need — that is your TDEE, your BMR multiplied by an activity factor. For losing or gaining weight, set your target from TDEE, not BMR. See BMR vs TDEE for the difference.
Common questions
What is the most accurate BMR calculator?
One built on the Mifflin-St Jeor equation. A 2005 systematic review found it predicted measured resting metabolism within 10% for more people than older formulas like Harris-Benedict — which is why dietitians use it as the default. This calculator uses it.
What is a normal BMR?
There is no single normal figure — BMR scales with your size, age and sex. As a reference point, the Mifflin-St Jeor equation gives a 30-year-old woman of 165 cm and 65 kg a BMR of about 1,370 kcal/day, and a 30-year-old man of 180 cm and 80 kg about 1,780. What matters is your own number and how it changes over time, not how it compares to anyone else.
What is a normal BMR for a woman?
Most adult women fall roughly between 1,200 and 1,600 calories a day at rest, depending on size and age — for example the equation gives a 30-year-old woman at 165 cm and 65 kg about 1,370. Women’s values run lower than men’s mainly because of average differences in body size and lean mass, which is why the equation’s constant is −161 for women versus +5 for men.
How many calories should I eat if my BMR is 1,500?
More than 1,500. Multiply your BMR by your activity factor to get your TDEE — at a moderate activity level, 1,500 × 1.55 ≈ 2,325 calories to maintain your weight. To lose weight, subtract 300–500 from that TDEE (≈1,825–2,025), not from your BMR. The same logic applies to any BMR.
Should I eat at my BMR to lose weight?
No. Your BMR is what you burn at complete rest, before any activity — so eating at exactly your BMR usually means a very large deficit once daily movement is added. Base weight-loss calories on your TDEE instead, with a modest deficit.