Calorie Deficit Calculator

BMR (Basal Metabolic Rate) is calories your body burns at complete rest — breathing, circulation, cell repair. TDEE (Total Daily Energy Expenditure) = BMR × activity multiplier. A sedentary person burns BMR × 1.2; a very active person burns BMR × 1.725. Your TDEE is your maintenance calorie level — eat below it to lose weight, above it to gain. Most calculators use the Mifflin-St Jeor equation (±10% accuracy).

1 lb (0.45 kg) of body fat ≈ 3,500 calories. A 500 calorie/day deficit = ~1 lb/week loss. Safe weight loss range: 0.5–1 kg/week. Below 1,200 kcal/day (women) or 1,500 kcal/day (men) risks muscle loss and nutrient deficiency. For muscle gain: a 250–500 calorie surplus with adequate protein (1.6–2.2g per kg bodyweight) produces lean mass with minimal fat gain.

Sedentary (×1.2): desk job, no exercise. Lightly active (×1.375): 1-3 days/week light exercise. Moderately active (×1.55): 3-5 days/week moderate exercise. Very active (×1.725): 6-7 days/week hard exercise. Extra active (×1.9): physical job + hard exercise daily. Most people overestimate their activity level — when in doubt, choose one level lower and adjust based on real results over 2-3 weeks.

Calorie labels have up to ±20% error (FDA allowance). Food preparation (cooking, chopping) changes calorie density. Individual metabolic rate varies ±15% from calculator estimates due to genetics, gut microbiome, and hormones. Tracking trends over 2+ weeks is more useful than daily numbers. If the scale does not move after 2-3 weeks at a deficit, reduce calories by 100-150/day rather than making large sudden cuts.