The arithmetic of a deficit
A kilogram of body fat stores roughly 7,700 kcal. To lose 0.5 kg per week you therefore need a weekly shortfall of ~3,850 kcal — about 550 per day. This calculator does that conversion from your own TDEE, so the daily number is personal rather than generic. The full reasoning is in our calorie deficit explainer.
Choosing a rate
Bigger deficits lose faster on paper but cost more muscle, suppress NEAT, and break adherence — the actual rate-limiter for almost everyone. A useful rule: aim to lose no more than 0.5–1% of body weight per week, using the lower end as you get leaner. Our guides to a 500-calorie and 1,000-calorie deficit walk through what each feels like in practice. And if a flat number is hard to live with, the calorie cycling calculator rebuilds the same weekly deficit as a 7-day wave around your training days.
Frequently asked questions
Is a 500 calorie deficit good?
It's the standard recommendation for a reason: meaningful progress (~0.5 kg/week) at a restriction level most people can actually sustain, with modest muscle-loss risk if protein and training are in place.
Why has my weight loss stalled in a deficit?
Three usual suspects: water retention masking fat loss (very common around stress and hard training), intake creeping above target, or TDEE falling as you get lighter. Re-run the calculator at your new weight every 4–5 kg.
Can a deficit be too big?
Yes. Beyond ~25% below TDEE, muscle loss accelerates, NEAT drops, and hunger rebounds — many people end up losing less over six months than they would on a moderate deficit they could actually keep.
More calculators
TDEE Calculator
Work out your Total Daily Energy Expenditure
Calorie Calculator
Get a daily calorie target matched to your goal
BMR Calculator
Estimate the calories your body burns at complete rest, compared across the three standard equations
Macro Calculator
Split your daily calories into protein, carbs and fat
Maintenance Calorie Calculator
Find the daily calories that keep your weight stable
Weight Loss Calculator
See your realistic goal date
Sources
- Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958. [link]
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011. [link]
- Leibel RL, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med. 1995. [link]