Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions — breathing, circulation, cell production, temperature regulation, and organ function. BMR accounts for approximately 60–70% of total daily calorie expenditure in sedentary individuals and represents the minimum energy your body requires to survive.

BMR is calculated using validated equations that factor in weight, height, age, and sex. This calculator uses the Mifflin-St Jeor equation (1990), which is considered the most accurate predictor of resting metabolic rate for the general population according to the Academy of Nutrition and Dietetics — more accurate than the older Harris-Benedict equation (1919) it largely replaced.

BMR is the foundation for calculating TDEE (Total Daily Energy Expenditure). To find your maintenance calories, BMR is multiplied by an activity factor. Understanding your BMR helps you set accurate calorie targets for weight loss, maintenance, or muscle gain without guesswork.