Harris-Benedict BMR Calculator
Calculate basal metabolic rate using the Harris-Benedict equation.
Enter sex, age, weight, and height to estimate daily calorie needs at rest and with activity.
The Harris-Benedict equation estimates your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest just to keep you alive. Heart beating, lungs breathing, liver processing — all of that has an energy cost, even in bed.
The revised 1984 Mifflin-St Jeor equation is now considered more accurate for most people, but Harris-Benedict (originally published in 1918, revised in 1984) remains widely used and taught:
For men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age)
For women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age)
Multiply BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE):
- Sedentary (desk job, no exercise): BMR x 1.2
- Lightly active (light exercise 1-3 days/week): BMR x 1.375
- Moderately active (moderate exercise 3-5 days/week): BMR x 1.55
- Very active (hard exercise 6-7 days/week): BMR x 1.725
- Extra active (physical job + daily training): BMR x 1.9
BMR accounts for roughly 60-70% of total daily energy expenditure for most people. Physical activity adds 15-30%, and the thermic effect of food (digesting your meals) adds another 10%.
The equations are population averages with meaningful individual variation. Actual BMR can differ from the formula by 10-15% depending on genetics, hormones, lean muscle mass, and other factors. If you are tracking calories and not losing weight as expected, your actual BMR is likely lower than the formula predicts.