BMR Calculator

Basal Metabolic Rate (BMR) is the number of calories your body needs each day just to keep itself running — breathing, circulating blood, repairing cells, and maintaining body temperature — with no movement or digestion included. It's the energy cost of simply being alive, measured at complete rest.

This calculator uses the Mifflin-St Jeor equation, developed by Mifflin and St Jeor in 1990 and now the formula recommended by the Academy of Nutrition and Dietetics for most adults, having replaced the older Harris-Benedict equation from 1919. It calculates BMR from your weight, height, age, and sex, since sex affects the equation because men typically carry more lean muscle mass than women at the same weight and height, and muscle tissue burns more calories at rest than fat tissue does.

Your BMR is a starting point, not your full calorie need. To find out how many calories you actually burn in a day, BMR gets multiplied by an activity factor that accounts for exercise, daily movement, and the energy your body spends digesting food — that total is called Total Daily Energy Expenditure (TDEE). Like any predictive formula, Mifflin-St Jeor gives a population-average estimate; individual factors like genetics, muscle mass, and hormone levels can shift your real BMR up or down from what's shown here.