TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including your basal metabolic rate, physical activity, and the thermic effect of food. It determines how many calories you need to maintain, lose, or gain weight. Knowing your TDEE is the foundation of any nutrition plan.
This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate for estimating BMR. The formula is: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5 (male) or -161 (female). Your TDEE is then BMR multiplied by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active).
Research consistently shows 0.7-1g of protein per pound of bodyweight is optimal for muscle building. This calculator recommends 1g/lb for muscle gain goals and 0.8g/lb for maintenance. If you're in a calorie deficit, higher protein (1g/lb) helps preserve muscle mass while losing fat.
For fat loss, eat 300-500 calories below your TDEE (a moderate deficit preserves muscle). For muscle gain, eat 200-400 calories above TDEE. For body recomposition (losing fat while gaining muscle), eat at maintenance with high protein. Beginners and overweight individuals can often recomp effectively.
The Mifflin-St Jeor equation is accurate to within 10% for most people. Your actual TDEE depends on factors like genetics, NEAT (non-exercise activity), and metabolic adaptation. Use this as a starting point, then adjust based on real-world results over 2-3 weeks. If your weight isn't changing as expected, adjust by 100-200 calories.