Calorie Deficit Calculator

Daily deficit = target weekly loss (kg) × 7,700 ÷ 7. Target calories = maintenance (TDEE) − deficit. The deficit is capped at 25% of maintenance, and the target is floored at your BMR.

Hall KD et al. (2011) Lancet — dynamic model of human energy balance; 7,700 kcal ≈ 1 kg of body mass.

Real loss runs slower than the arithmetic as weight, water, and metabolism shift. Recalibrate every 3–4 weeks against your actual weekly change.

People under 18, anyone with a BMI below 18.5, and people who are pregnant, breastfeeding, or managing an eating disorder. The tool suppresses a deficit when BMI is already low.

A calorie deficit means eating fewer calories than your body burns in a day. When you're in a deficit, your body makes up the difference by using stored energy — primarily fat — which is how weight loss happens.

A deficit of 15–25% below your maintenance calories is a sustainable range for most people. This calculator caps the deficit at 25% and never drops your target below your BMR, because larger deficits tend to cost muscle, tank energy, and rebound.

Roughly 7,700 calories per kilogram (about 3,500 per pound). So a 550 kcal daily deficit adds up to about 0.5 kg of loss per week — though real-world loss is a bit slower because of water and metabolic adjustments.

Two safety floors are built in and can't be bypassed: your target never falls below your BMR, and the deficit is capped at 25% of maintenance. If your BMI is already in the underweight range, it won't suggest a deficit at all.

The 7,700 kcal-per-kg math is a simplification. As you lose weight your maintenance falls, water balance shifts, and adherence varies. Expect real loss to trail the estimate slightly, and recalculate every 3–4 weeks.

No — a deficit can come entirely from eating less. Exercise helps by increasing the calories you burn (raising the maintenance side) and by preserving muscle, but the deficit itself is about the gap between intake and expenditure.