BMR Calculator

Understanding Basal Metabolic Rate

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain essential functions — breathing, circulation, cell production, and temperature regulation. It represents roughly 60–75% of total daily calorie expenditure for most people. The Mifflin-St Jeor equation (developed in 1990) is widely considered the most accurate for the general population, while the revised Harris-Benedict equation (1984) remains a reliable alternative. Both use your weight, height, age, and biological sex. To get your Total Daily Energy Expenditure (TDEE), multiply BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active).

Knowing your BMR is the foundation of any nutrition plan. If your goal is fat loss, eating 300–500 kcal below your TDEE creates a sustainable deficit. For muscle gain, a surplus of 250–500 kcal above TDEE is typically recommended. Pairing your BMR with a macro calculator ensures you hit not just calorie goals but also the right protein, carbohydrate, and fat targets.

BMR can change over time due to aging (decreasing ~1–2% per decade after 25), changes in muscle mass, hormonal shifts, and diet history. Crash dieting can lower BMR through adaptive thermogenesis. Resistance training helps preserve or increase metabolic rate. Because individual metabolisms vary, these formulas provide excellent starting estimates — track your actual weight change over 2–3 weeks and adjust intake accordingly. Always consult a healthcare provider or registered dietitian for personalized guidance.

For informational purposes only. This calculator does not constitute medical advice.