Calorie Deficit Calculator
The daily calorie deficit to reach a target weight within a set number of weeks.
Result
Weight to lose
5.0
Daily deficit (kcal)
550
How it works
Losing fat requires eating less energy than you spend, and the gap is the deficit. Body fat stores roughly 7,700 kcal per kilogram, so shedding one kilo means accumulating about that much shortfall — this calculator spreads the total across your chosen timeframe to give a daily target. A sustainable deficit sits around 300–500 kcal a day, which yields roughly 0.3–0.5 kg per week. Pushing to 1,000 kcal doubles the speed on paper but rarely in practice: very aggressive deficits cost muscle, tank energy and appetite control, and are the main reason diets are abandoned. Expect the scale to lie in the short term. Water, glycogen, salt and digestive contents swing daily weight by a kilo or more in either direction, which easily masks real fat loss for a week or two. Judge progress on a weekly average, not on any single morning.
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Frequently asked questions
Is a big deficit safe?
Aim for 0.5–1 kg per week; very large deficits are hard to sustain and can cost muscle.
Why 7700 kcal per kg?
That is the approximate energy stored in a kilogram of body fat.
Should the deficit come from eating less or moving more?
Mostly from food — it is far easier to not eat 400 kcal than to burn it. Exercise still matters: it preserves muscle during the deficit and improves health, so use it alongside, not instead.
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