What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns. The gap is made up from stored energy, mostly body fat, so your weight goes down. You can create a deficit by eating less, moving more, or both.
Daily deficit = (current weight − goal weight) × 7,700 kcal ÷ days until target
One kilogram of body weight lost is worth roughly 7,700 kcal (about 3,500 kcal per pound). That figure is an average. Early on, more of the loss is water, so the scale moves faster than the maths suggests.
How big should my deficit be?
| Daily deficit | Expected loss per week | Good for |
|---|---|---|
| 250–300 kcal | 0.25 kg (0.5 lb) | Near your goal weight, or building muscle at the same time |
| 500 kcal | 0.5 kg (1 lb) | Most people. Steady and sustainable |
| 750 kcal | 0.75 kg (1.5 lb) | Higher starting weight, short-term push |
| 1,000+ kcal | 1 kg (2 lb) or more | Only with a lot to lose, ideally with medical support |
If your target date needs more than about 1% of your body weight per week, the calculator suggests a more realistic date instead.
Making a deficit easier to stick to
- Eat protein at every meal. It is the most filling macro and helps you keep muscle.
- Fill half the plate with vegetables or salad. Lots of volume, few calories.
- Watch liquid calories: sugary drinks, juices, alcohol and large milky coffees add up fast.
- Walk more. An extra 3,000 steps a day burns roughly 100–150 kcal without making you hungrier.
- Plan breaks. Some people do well with a week at maintenance every 8 to 12 weeks.
Read more in our guide to how a calorie deficit works.
Frequently asked questions
How long does it take to see results in a calorie deficit?
Most people see the scale move in the first one to two weeks, partly from water. Visible changes in the mirror often take four to eight weeks of consistent eating.
Why am I not losing weight in a deficit?
The most common reasons are underestimating portions, weekend eating, drinks, and water retention hiding fat loss. Track honestly for two weeks and compare weekly average weights rather than single days.
Is a 1,000 calorie deficit safe?
For people with a lot of weight to lose it can be, for a limited time. For most people it is too aggressive and risks muscle loss, fatigue and rebound eating. A 500 kcal deficit is a more sustainable default.
Reviewed and updated 22 October 2026. See how we calculate.