BMR Calculator
Enter your sex, age, height and weight to see how many calories your body burns at rest and how that scales with your activity level.
Enables the Katch-McArdle formula.
- Mifflin-St Jeor (1990)
- 1,783 kcal
- Harris-Benedict (revised 1984)
- 1,865 kcal
- Katch-McArdle
- Enter body fat %
- Lean body mass
- —
| Activity level | Factor | Calories/day |
|---|---|---|
| Sedentary — Desk job, little or no exercise | × 1.2 | 2,139 |
| Lightly active — Light exercise 1–3 days a week | × 1.375 | 2,451 |
| Moderately active — Moderate exercise 3–5 days a week | × 1.55 | 2,763 |
| Active — Hard exercise 6–7 days a week | × 1.725 | 3,075 |
| Very active — Hard daily exercise plus a physical job | × 1.9 | 3,387 |
How this was calculated
- Convert to metric: weight W = 81.6 kg, height H = 177.8 cm, age A = 30 years.
- Mifflin-St Jeor (men): BMR = 10 × 81.6 + 6.25 × 177.8 − 5 × 30 + 5 = 1,783 kcal/day.
- Harris-Benedict (revised, men): 88.362 + 13.397 × 81.6 + 4.799 × 177.8 − 5.677 × 30 = 1,865 kcal/day.
- TDEE = BMR × activity factor, e.g. moderately active: 1,783 × 1.55 = 2,763 kcal/day.
BMR formulas are population averages and can be off by 10% or more for an individual. This is an estimate for general information, not medical advice.
How this BMR calculator works
Your basal metabolic rate (BMR) is the number of calories your body burns in 24 hours just to stay alive: breathing, pumping blood, keeping warm, repairing cells. It is what you would burn lying in bed all day without eating. This BMR calculator uses the Mifflin-St Jeor equation as its headline number because a 2005 review by the Academy of Nutrition and Dietetics found it the most accurate of the common formulas for people of normal and above-normal weight. It then shows the revised Harris-Benedict and, if you enter a body-fat percentage, Katch-McArdle, so you can see how much the methods disagree.
Mifflin-St Jeor is BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men and the same with − 161 instead of + 5 for women. Harris-Benedict weights the inputs differently and tends to run a few percent higher. Katch-McArdle ignores sex and age entirely and works from lean body mass: BMR = 370 + 21.6 × lean mass in kg. It is the better choice if you are unusually muscular or carry a lot of fat, because the other two assume an average body composition for your size.
Worked example
A 30-year-old man who is 180 cm (5'11") and 80 kg (176 lb): 10 × 80 = 800, plus 6.25 × 180 = 1,125, minus 5 × 30 = 150, plus 5, gives a BMR of 1,780 kcal per day. Harris-Benedict gives 1,854. If he knows he is at 20% body fat, his lean mass is 64 kg and Katch-McArdle gives 370 + 21.6 × 64 = 1,752. All three land within about 100 calories of each other, which is typical.
Nobody actually lies in bed all day, so the table under the result multiplies BMR by an activity factor to get total daily energy expenditure (TDEE), the calories you need to hold your weight steady. For the man above, a desk job with no exercise (× 1.2) means about 2,136 kcal; training hard most days (× 1.725) means about 3,070 kcal.
Common mistakes
- Eating at your BMR to lose weight. BMR is a floor, not a target. Most people's real needs are 1.3 to 1.7 times higher, and eating at BMR for long is hard to sustain.
- Picking too high an activity level. Three gym sessions a week on top of a desk job is "lightly active", not "moderately active". Overestimating activity is the most common reason a calorie target fails.
- Entering inches as decimal feet. 5 feet 10 inches is 5 ft and 10 in, not 5.10 ft. Use the two separate boxes or switch to centimeters.
When the number is misleading
All three formulas are regressions fitted to groups of people, so your true BMR can sit 10% or more away from the estimate; measured values in the lab vary that much even among people of identical size. Thyroid conditions, pregnancy, recent large weight loss, very low or very high body fat, and age over about 70 all push real metabolism away from the formula. Treat the result as a starting point: hold your intake steady for two to three weeks, watch the scale, and adjust by 100 to 200 calories rather than trusting any formula to the last digit.
Frequently asked questions
›What is basal metabolic rate?
BMR is the number of calories your body burns in 24 hours at complete rest to keep organs working, breathe and stay warm. It is typically 60–70% of the calories an adult burns in a day.
›What is the Mifflin-St Jeor formula?
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. A 30-year-old man of 180 cm and 80 kg has a BMR of 1,780 kcal per day.
›What is the difference between BMR and TDEE?
TDEE (total daily energy expenditure) is BMR multiplied by an activity factor from 1.2 (sedentary) to 1.9 (very active). It is the number of calories that keeps your weight stable, so it is the one to use for diet planning.
›Which BMR formula is most accurate?
Mifflin-St Jeor is the most accurate for most adults according to a 2005 Academy of Nutrition and Dietetics review. Katch-McArdle is better if you know your body-fat percentage and are very lean or very muscular.
›Should I eat at my BMR to lose weight?
No. BMR is the minimum your body uses at rest; eating that little is hard to sustain and often below the 1,200–1,500 kcal floor recommended for unsupervised dieting. Subtract 250–500 kcal from your TDEE instead.