What is a calorie deficit?
A calorie deficit means taking in less energy than your body uses. The missing energy comes from your reserves – mainly fat. How much you use depends on your BMR and activity, which the calorie calculator works out.
Rule of thumb: about 7,700 kcal equal roughly one kilogram of body weight. A 500 kcal daily deficit adds up to 3,500 kcal a week – about half a kilo.
How big should your deficit be?
For most people a deficit of 300–500 kcal a day works well: enough for visible progress without constant hunger.
| Daily deficit | Weekly loss (approx.) | Suitable for |
|---|---|---|
| 250–300 kcal | 0.25 kg | gentle start, little hunger |
| 500 kcal | 0.5 kg | the usual guideline |
| 750–1,000 kcal | 0.75–1 kg | only with significant excess weight |
The calculator always stays within these limits: at most 25 % below your needs, at most 1 % of body weight per week and never below 1,200 kcal (women) or 1,500 kcal (men).
Why too big a deficit backfires
- Muscle loss: with too little energy your body breaks down muscle, lowering your BMR.
- Cravings: eating too little for long rarely lasts.
- Yo-yo effect: after a crash diet the weight often comes back quickly.
- Nutrient gaps: very few calories make it hard to get enough protein, vitamins and minerals.
Deficit through food or exercise?
Both work. Food is easier to control; exercise helps keep muscle and gives you more room. Just don't count regular training twice: if it's already in your activity level, don't eat the burned calories on top.
Why the scale sometimes stalls
Water, salt and stomach contents make your weight swing by up to 1–2 kg a day. Only the trend over two to four weeks shows whether your deficit works. And as you lose weight your needs drop, so the same food gives a smaller deficit – recalculate every few kilos.
The free calorie counter does this automatically: it compares your food with your actual weight trend and shows a forecast range instead of a fixed target date.