Calorie Deficit Calculator
Losing fat comes down to eating less energy than you spend, consistently, for long enough to matter. The arithmetic is simple; picking a rate you can actually live with is the hard part.
This calculator works out your maintenance calories, subtracts the deficit for the rate you choose, and refuses to hand you a number below what is safe to eat.
This is an estimate for healthy adults, not medical advice. If you are pregnant, breastfeeding, or managing a medical condition, speak to your doctor before acting on it.
How it works
A kilogram of body fat holds roughly 7,700 kcal, so losing half a kilogram a week needs about a 550 kcal daily deficit. We subtract that from your TDEE. If the result falls below 1,200 kcal for women or 1,500 kcal for men, we raise it to that floor and tell you we did.
target = TDEE - ((kg per week x 7,700) / 7)
A worked example
A TDEE of 2,602 kcal with a goal of half a kilogram a week: 0.5 x 7,700 = 3,850 kcal a week, or 550 a day. The target is 2,602 - 550 = about 2,052 kcal a day.
What it cannot tell you
- Weight moves for reasons that have nothing to do with fat: water, salt, glycogen and the state of your gut can swing the scale by a kilogram or more in a day.
- The 7,700 kcal figure is an approximation. Real loss slows as you get lighter, because a smaller body burns less.
- Very aggressive deficits cost muscle as well as fat and are harder to sustain. A slower rate you can keep to beats a fast one you abandon.
Frequently asked
- What is a safe calorie deficit?
- For most people, 300 to 550 kcal a day, giving roughly 0.25 to 0.5 kg of loss a week. Larger deficits work but get harder to sustain and cost more muscle.
- Why will the calculator not go below 1,200 or 1,500 calories?
- Below those levels it becomes difficult to get enough protein, vitamins and minerals from food. If your maths points lower, the answer is to move more rather than eat less.
- How long before I see a change?
- Real fat loss shows over weeks, not days. Weigh yourself at the same time under the same conditions and judge by the trend across two to three weeks.
- Do I need to count calories forever?
- No. Most people count for a while to learn what portions actually look like, then rely on that judgement afterwards.