Calorie Deficit Calculator

Enter your Total Daily Energy Expenditure (TDEE) — the total calories your body burns in a day at your current activity level — along with your target weekly weight loss, and this calculator works backward to give you a precise daily calorie target and the deficit required to achieve it. Understanding your calorie deficit is the foundation of any evidence-based fat loss plan. The math is grounded in the well-established principle that one kilogram of body fat stores approximately 7,700 kilocalories of energy; losing that fat requires creating a cumulative deficit of that many calories through some combination of reduced intake and increased activity. A daily deficit of 550 calories produces a weekly deficit of 3,850 calories — equivalent to approximately 0.5 kg of fat loss per week. Nutrition professionals generally recommend a deficit of 300–750 kcal per day for sustainable fat loss without triggering excessive muscle loss, nutrient deficiencies, or metabolic adaptation — your body's tendency to lower its resting metabolic rate in response to severe caloric restriction. Aggressive deficits above 1,000 kcal per day are associated with faster initial weight loss but also greater lean mass loss and higher rates of rebound weight gain after the diet ends. This calculator enforces a minimum floor of 1,000 kcal per day to flag potentially unsafe targets. Pair this tool with a TDEE or calorie calculator to establish your maintenance calories, then use this output to set a daily eating target.

The formula proceeds in three steps. Step 1: compute the weekly calorie deficit required for the target weight loss — weekly deficit = target kg × 7,700 kcal. Step 2: convert to a daily figure by dividing by 7. Step 3: subtract the daily deficit from TDEE — daily calorie target = TDEE − (weekly deficit ÷ 7). Worked example: TDEE of 2,500 kcal/day, target loss of 0.5 kg/week. Weekly deficit = 0.5 × 7,700 = 3,850 kcal. Daily deficit = 3,850 ÷ 7 = 550 kcal. Daily calorie target = 2,500 − 550 = 1,950 kcal/day. The 7,700 kcal/kg figure is the most widely cited estimate of the energy content of one kilogram of human adipose tissue. The actual value ranges from approximately 7,400–7,900 kcal/kg depending on body composition and hydration status, so real-world fat loss varies slightly from the mathematical prediction. The 1,000 kcal/day floor flags targets falling below a clinically recognized safety threshold; most practitioners set this floor higher at 1,200–1,500 kcal/day depending on body size, but 1,000 kcal represents the minimum used in medically supervised programs.