Your Calorie Deficit & TDEE Calculator

TDEE stands for Total Daily Energy Expenditure — the total number of calories your body burns in a day, including exercise. To lose fat you need to eat below your TDEE (a deficit), and to gain muscle you eat above it. Knowing your TDEE is the single most important number for body composition change.

A moderate deficit of 300–500 kcal/day (roughly 0.5 kg/week loss) is considered the optimal zone: fast enough to see results, slow enough to preserve muscle and energy. Aggressive deficits (500–750 kcal/day) work but carry a higher risk of muscle loss, fatigue and rebound. Never go below your BMR without medical supervision.

When you eat in a calorie deficit, your body can break down muscle tissue for energy — a process called catabolism. High protein intake (1.6–2.2 g per kg of bodyweight) stimulates muscle protein synthesis and dramatically reduces muscle loss during fat loss. This is even more critical on GLP-1 medications where appetite suppression makes hitting protein targets harder.

We use the Mifflin-St Jeor equation, considered the most accurate BMR formula for the general population (±10% error vs. measured metabolic rate). Real-world results depend on your actual activity, metabolic adaptations and food tracking accuracy. Use these numbers as a starting point and adjust after 2–3 weeks based on actual weight trend.

The US Navy circumference method (Hodgdon & Beckett, 1984) estimates body fat percentage from height, neck, waist and hip (females only) measurements. It's validated to ±2–3% accuracy for most people — comparable to bioelectrical impedance scales but far cheaper. A DEXA scan remains the gold standard for precise body composition analysis.