BMR Calculator
Enter your weight, height, age, and sex to estimate your basal metabolic rate (BMR), the calories your body burns at complete rest. This calculator uses the Mifflin-St Jeor equation, the formula most dietitians consider the most accurate available.
How to calculate bmr
The Mifflin-St Jeor equation estimates the calories your body needs at complete rest to keep your organs and systems running. Multiply weight in kilograms by 10, height in centimeters by 6.25, and age in years by 5, then combine them with a sex-specific constant (add 5 for men, subtract 161 for women). It replaced the older Harris-Benedict equation because it matches measured resting energy expenditure more closely in modern populations.
Male: BMR = 10W + 6.25H - 5A + 5. Female: BMR = 10W + 6.25H - 5A - 161 (W in kg, H in cm, A in years)
Worked example
A 30-year-old man weighs 180 lb (81.65 kg) and is 5 ft 10 in (70 in, 177.8 cm) tall.
- Weight: 180 lb x 0.453592 = 81.65 kg
- Height: 70 in x 2.54 = 177.8 cm
- 10 x 81.65 = 816.5
- 6.25 x 177.8 = 1,111.25
- 5 x 30 = 150
- BMR = 816.5 + 1,111.25 - 150 + 5 = 1,782.7
Result: A BMR of about 1,783 calories per day.
Frequently asked questions
What is BMR?
Basal metabolic rate is the number of calories your body burns at complete rest just to keep your heart, brain, and organs functioning. It does not include any calories burned through movement, digestion, or exercise; those are added on top of BMR to get your total daily energy expenditure (TDEE).
Why does this calculator use the Mifflin-St Jeor equation?
Mifflin-St Jeor (1990) is widely regarded by dietitians and the Academy of Nutrition and Dietetics as the most accurate resting-metabolism formula for the general population, edging out the older Harris-Benedict equation in validation studies. It only needs weight, height, age, and sex, no body-fat measurement required.
Is BMR the same as the calories I should eat to lose weight?
No. BMR is your resting floor, not a target. To lose weight you generally eat below your total daily energy expenditure (TDEE), which adds activity on top of BMR. Eating at or below BMR itself is usually too aggressive; use the TDEE calculator to find a more realistic maintenance and deficit target.
Why do men and women have different BMR formulas?
Men typically carry more lean muscle mass relative to total body weight, and muscle burns more calories at rest than fat tissue. The Mifflin-St Jeor equation accounts for this with a different constant (+5 for men, -161 for women) rather than requiring a separate body-fat measurement.
How accurate is a BMR calculator?
Formula-based BMR is an estimate, typically within about 10% of a lab measurement (indirect calorimetry) for most people. It is a reliable starting point for nutrition planning, but individual metabolism varies with muscle mass, genetics, and hormone levels. This tool is for general guidance, not medical advice.