Calculate your calorie deficit to lose weight
A calorie deficit means eating fewer calories than you burn. The calculator estimates your daily expenditure (your maintenance), shows you how much to eat with different deficits and how much you would lose to start with, never going below a safe minimum.
An estimate from published equations, not medical advice. If you are pregnant, breastfeeding, under 18 or have a medical condition, talk to a professional.
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How is a calorie deficit calculated?
First your maintenance is estimated: basal metabolic rate with the Mifflin-St Jeor equation (1990) multiplied by an activity factor from 1.2 to 1.9. Then the deficit is subtracted. The 2013 AHA/ACC/TOS guideline (Jensen et al.) recommends a deficit of 500 or 750 kcal a day. With the 7,700 kcal-per-kilo rule of thumb, 500 kcal less a day is about 0.45 kg a week to start with; the pace slows as you lose weight, because you burn less (Hall, 2008). An example: a 35-year-old woman, 1.65 m and 65 kg with moderate activity has a basal rate of 1,345 kcal and a maintenance of 2,085 kcal; with 500 kcal less she would eat 1,585 kcal a day. With light activity, her maintenance drops to 1,849 kcal and her floor is 1,480 kcal, so the largest deficit is 369 kcal: there is no room for 500. That floor (basal rate × 1.1 and never under 1,200 kcal for women or 1,400 for men) is the same one the app uses.
How much to eat with a 500 kcal deficit (two examples)
Maintenance → calories for a 500 kcal daily deficit, by activity level. Two 35-year-old profiles calculated with the same formula as the calculator: a woman of 1.65 m and 70 kg and a man of 1.78 m and 85 kg.
| Activity | Woman 1.65 m · 70 kg | Man 1.78 m · 85 kg |
|---|---|---|
| Sedentary (×1.2) | 1674 → 1535 kcal (floor) | 2152 → 1972 kcal (floor) |
| Light, 1-3 days (×1.375) | 1918 → 1535 kcal (floor) | 2465 → 1972 kcal (floor) |
| Moderate, 3-5 days (×1.55) | 2162 → 1662 kcal | 2779 → 2279 kcal |
| High, 6-7 days (×1.725) | 2406 → 1906 kcal | 3093 → 2593 kcal |
| Very high (×1.9) | 2651 → 2151 kcal | 3407 → 2907 kcal |
Maintenance with Mifflin-St Jeor (1990) times the activity factor. “(floor)”: a 500 kcal deficit does not fit without going below basal rate × 1.1 (minimum 1,200 kcal for women and 1,400 for men), so it stays at that floor and the real deficit is smaller. These are reference ranges for healthy adults, not a diagnosis or individual advice.
FAQ
How big should my calorie deficit be?
The 2013 AHA/ACC/TOS guideline suggests a deficit of 500 or 750 kcal a day, which to start with means about 0.45-0.7 kg a week. If, with your activity, that takes you below your floor, the deficit has to be smaller; moving more widens the margin without eating less.
What deficit do I need to lose a kilo?
As a rule of thumb, about 7,700 kcal per kilo: losing 1 kg in a week would take about 1,100 kcal less a day, too much for almost everyone. The rule is an approximation: Hall (2008) showed it fits people with a lot of body fat and overstates the energy in each kilo in leaner people.
Why am I in a deficit and not losing weight?
The usual causes: water (weight swings by several hundred grams from day to day), logging less than you eat and a real expenditure lower than the estimate. Watch the trend over 2-3 weeks, not a single weigh-in, and work out your real expenditure from what you eat and how your weight changes with the TDEE calculator.
Can I build muscle in a calorie deficit?
Gaining a lot of muscle in a deficit is hard, but keeping it is doable: train strength and eat enough protein. To find out how much, use the protein calculator; to split the rest of your calories, the macro calculator.
Keep reading
- Calorie deficit for beginners →
- How many calories should I eat a day →
- 1,500 calorie meal plan: 7 days →
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