BMR Calculator

What Is BMR and How Is It Calculated?

Basal Metabolic Rate (BMR) represents the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, cell production, and temperature regulation. This calculator uses the Mifflin-St Jeor equation, which the American Dietetic Association considers the most accurate predictive formula for resting metabolism in healthy adults. For men, the formula is 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age in years plus 5. For women, the final constant is minus 161 instead of plus 5. BMR typically accounts for 60 to 75 percent of your total daily energy expenditure, making it the foundation for any calorie-based nutrition plan. Knowing your BMR helps you set realistic calorie targets for weight loss, maintenance, or muscle gain.

Why BMR Matters for Weight Loss and Muscle Gain

Your BMR is the starting point for every evidence-based nutrition strategy. If you eat below your BMR for extended periods, your body can adapt by downregulating thyroid hormones and reducing non-exercise activity, slowing further fat loss. If you eat substantially above your maintenance calories, the surplus beyond what muscle protein synthesis can use gets stored as fat. BMR also changes over time. Age reduces resting metabolism by roughly 1 to 2 percent per decade after 20, mostly because of lean mass loss. Building muscle through resistance training is one of the few reliable ways to raise BMR, since each kilogram of lean tissue burns approximately 13 kilocalories per day at rest. Use your BMR as a floor value and add activity-based calories to determine your true daily energy needs.

Frequently Asked Questions