Daily Calorie Deficit Calculator
Turn a weekly weight-loss goal into a daily calorie deficit and eating target from your maintenance calories, with a timeline to your goal.
How it works
Daily deficit = (weekly loss kg × 7700 kcal) ÷ 7 · Daily target = TDEE − daily deficit · Weeks to goal = weight to lose ÷ weekly loss · (~7700 kcal ≈ 1 kg of body fat)
Sustained weight loss comes from eating fewer calories than you burn, and roughly 7,700 kcal is stored in a kilogram of body fat (about 3,500 kcal per pound). Dividing the weekly energy gap by seven gives the daily deficit you subtract from your maintenance calories, or TDEE, to get an eating target. This linear model is a useful planning guide, but real loss slows over time as your body adapts and maintenance falls, so recalculate as your weight changes and keep intake at a sensible floor.
Worked example
At a 2,500 kcal maintenance and a 0.5 kg/week goal: daily deficit = 0.5 × 7700 ÷ 7 = 550 kcal, so the target is 2,500 − 550 = 1,950 kcal/day. To lose 5 kg takes 5 ÷ 0.5 = 10 weeks.
Sources: Energy content of body fat
Frequently asked questions
How big a deficit is safe?
A deficit that loses about 0.5–1% of body weight per week is a common guideline, and most authorities suggest not dropping below roughly 1,200 kcal/day for women or 1,500 for men without supervision. Slower loss is easier to sustain and protects muscle.
Why does weight loss slow down?
As you lose weight your body needs fewer calories, so a fixed intake becomes a smaller deficit over time. Metabolic adaptation reduces expenditure further, which is why targets should be recalculated periodically.
Is the 7,700 kcal per kg figure exact?
It is an approximation based on the energy in body fat. Real losses also include water and some lean tissue early on, so the timeline is an estimate rather than a guarantee.
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Educational estimate using standard published formulas — not medical advice, a diagnosis, or a substitute for clinical judgement. Dosing, diagnosis and treatment must be decided by a qualified clinician using validated tools and the full clinical picture.