What a calorie deficit is
A deficit is eating below your maintenance calories so your body draws on stored energy. Roughly 7,700 kcal is about a kilogram of fat, so a 500 kcal daily deficit is, in theory, near half a kilo a week. In practice the number wobbles — which is why the target here is a range, not a false-precise figure.
How big a deficit?
We show two, both built from your maintenance: gentle (−10%) and moderate (−20%). Past roughly a quarter below maintenance, more of what you lose is muscle and water, hunger and fatigue climb, and the rebound gets likelier. Choose the pace you could sustain for months, not the one that looks fastest this week.
The floor — why not go lower
Below about 1,200 kcal (women) or 1,500 (men) it becomes hard to get enough protein and micronutrients, and the plan gets harder to stick to — not easier. This tool holds your target at that floor instead of recommending less. And if you’re already in a healthy range, a deficit is a choice, not a necessity.
Keep the muscle
In any deficit, protein plus resistance training is what protects lean mass, so more of what you lose is fat. Set your intake with the protein calculator — it uses the same body-weight range, so the numbers line up across the site.
FAQ
How do I calculate a calorie deficit?
Start from maintenance (your TDEE), then subtract. Roughly 7,700 kcal is a kilo of body fat, so a 500 kcal daily deficit is about 0.45 kg a week — in theory. We show the deficit as a target range because your maintenance is a range, not a single number.
How big should my deficit be?
A gentle deficit is around 10% below maintenance; a moderate one about 20%. Bigger is not better: past roughly 20–25% you lose more muscle, feel worse, and are more likely to rebound. The pace you can hold for months beats the fastest one on paper.
Is a 500-calorie deficit good?
It is a common target and reasonable for many people — about 0.45 kg a week. But 500 kcal is a bigger share for a smaller person than a larger one, which is why a deficit set as a percentage of your own maintenance is more honest than a flat number.
What is the lowest I should eat?
Common guidance is not to drop below about 1,200 kcal a day for women or 1,500 for men without medical supervision — below that it is hard to get enough protein and micronutrients. This tool holds your target at that floor rather than recommending less.
Why am I not losing in a deficit?
Usually because the deficit is smaller than it looks — intake gets under-counted and activity over-counted. If the scale is flat for a few weeks, your real maintenance is lower than the estimate; see the maintenance page, and track honestly for two weeks.