BMR Calculator
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Calculate your Basal Metabolic Rate using the Mifflin-St Jeor and Harris-Benedict formulas. Find out how many calories your body burns at rest.
Enter your values below and click Calculate for instant results.
Basal metabolic rate (BMR) is the number of calories your body burns per day at complete rest, just to maintain basic life functions: breathing, circulation, cell production, temperature regulation, and organ function. It represents the minimum energy requirement to stay alive and accounts for the majority of most people's total daily energy expenditure.
For most people, BMR accounts for 60 to 75% of total daily calories burned. Physical activity typically accounts for 15 to 30%, and digesting food accounts for about 10%. This is why dramatically cutting calories without addressing the activity component has limited long-term effectiveness for weight management.
This calculator uses two established formulas. The Mifflin-St Jeor equation (1990) is considered more accurate for modern populations and is the formula most commonly recommended by the Academy of Nutrition and Dietetics. The Harris-Benedict equation (1919, revised in 1984) is older and tends to slightly overestimate BMR. This calculator shows both and averages them for a reliable midpoint estimate.
Muscle mass is the most significant factor. Muscle tissue burns more calories at rest than fat tissue, which is why people with more muscle mass have higher BMRs. Age also matters: BMR typically declines by 1 to 2% per decade after age 20, partly due to gradual muscle loss. Body size, sex (men generally have higher BMR than women at the same weight due to greater muscle mass), and thyroid function also play roles.