Calculate your Basal Metabolic Rate and daily calorie needs
Your Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, and cell production while at complete rest. This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate formula for estimating BMR.
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. It represents the total number of calories you burn per day including exercise and daily activities. Knowing your TDEE helps you plan nutrition for weight loss, maintenance, or muscle gain.
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just to keep you alive (breathing, circulation, cell production). It typically accounts for 60-75% of total daily energy expenditure. The most commonly used formulas are Mifflin-St Jeor (considered most accurate for most people) and Harris-Benedict (revised 1984). BMR depends on age (decreases ~2% per decade after 20), sex (men typically have higher BMR due to more muscle mass), weight, and height. Multiplying BMR by an activity factor gives your TDEE — the total calories you need daily. This is the foundation of any nutrition plan: eat below TDEE to lose weight, above to gain, at TDEE to maintain.
BMR is calories burned at complete rest. TDEE adds your activity level: sedentary (BMR×1.2), light exercise (×1.375), moderate (×1.55), heavy (×1.725), or athlete (×1.9). TDEE is what you actually need to eat daily.
The Mifflin-St Jeor equation (1990) is considered most accurate for most adults by the American Dietetic Association. It tends to be more accurate than Harris-Benedict, especially for overweight individuals.
Aging causes loss of lean muscle mass (sarcopenia) — about 3-8% per decade after 30. Since muscle is metabolically active tissue, less muscle means lower BMR. Resistance training helps slow this decline.
Yes — building muscle through resistance training is the most effective way. Each pound of muscle burns about 6 calories/day at rest versus 2 for fat. Regular exercise, adequate protein, and good sleep all support higher BMR.
BMR formulas are estimates with ~10% margin of error for most people. Individual variation due to genetics, hormones, gut microbiome, and body composition means actual BMR can differ. For precision, indirect calorimetry testing measures your actual metabolic rate.