Calorie deficit calculator
Enter where you are and where you want to be. You'll get the largest deficit that stays safe for your body, your daily target, and a realistic date.
- Safe daily deficit
- 645 kcal
- Daily target
- 1,934 kcal
- Around
- 96 days
What a calorie deficit actually is
A calorie deficit means eating less than you burn, so your body makes up the difference from its reserves. Roughly 7,700 kcal of deficit equals 1 kg of body fat (about 3,500 kcal per pound).
Bigger isn't better. Past a point, hunger wins, muscle goes along with fat, and the weight comes back. That's why this calculator caps the deficit three ways and picks the strictest limit for your body.
Making the date come true
The date assumes you hit your target most days. Two big weekend meals can cancel a week of careful days, so log those too, even roughly.
Recalculate every 3 to 5 kg. As you get lighter, maintenance drops, and yesterday's target slowly turns into maintenance.
How long 5 kg takes at the safe maximum
A 35-year-old woman, 165 cm (5 ft 5 in), walking but no sport, at different starting weights. Heavier bodies can lose faster without going below the safe limits.
| Starting weight | Maintenance | Safe daily deficit | Daily target | Time to lose 5 kg |
|---|---|---|---|---|
| 60 kg (132 lb) | 1,781 kcal | 445 kcal | 1,336 kcal | 12.4 weeks |
| 70 kg (154 lb) | 1,918 kcal | 480 kcal | 1,439 kcal | 11.6 weeks |
| 80 kg (176 lb) | 2,056 kcal | 514 kcal | 1,542 kcal | 10.7 weeks |
| 90 kg (198 lb) | 2,193 kcal | 548 kcal | 1,645 kcal | 10.1 weeks |
| 100 kg (220 lb) | 2,331 kcal | 583 kcal | 1,748 kcal | 9.6 weeks |
| 110 kg (243 lb) | 2,468 kcal | 617 kcal | 1,851 kcal | 9.0 weeks |
| 120 kg (265 lb) | 2,606 kcal | 651 kcal | 1,954 kcal | 8.6 weeks |
How it's calculated
First we find maintenance with Mifflin-St Jeor and your activity factor.
The safe daily deficit is the smallest of three numbers: 25% of maintenance, maintenance minus resting burn, and the deficit that loses 1% of your body weight per week.
Time to goal is the weight to lose × 7,700 kcal ÷ daily deficit. Real progress is rarely a straight line: water weight and a slower metabolism at a lower weight both shift it.
Example: a 35-year-old man, 180 cm, 92 kg, walking but no sport, aiming for 84 kg. Resting burn is 1,875 kcal and maintenance 2,578 kcal. The tightest cap here is 25% of maintenance, about 645 kcal a day, so his target is 1,934 kcal. 8 kg × 7,700 ÷ 645 is about 96 days, roughly 14 weeks.
Questions
How big should a calorie deficit be?
Big enough to see progress, small enough to keep up. For most adults that means a few hundred to about a thousand calories a day, and never so low that you eat below your resting burn.
Why does weight loss slow down?
A lighter body burns less, and early drops include water. Recalculate every few kilograms with your new weight.
Can teens use this?
No. We don't suggest a deficit under 18 or with a BMI under 18.5. Growing bodies need a doctor's plan, not a calculator's.
Let the app keep score
Kalorea sets your target with this formula and then counts every meal from a photo, so you can see each day where you stand.