Calorie Deficit Calculator
See the daily deficit needed to reach your goal weight in your chosen timeframe — and whether that pace is realistic.
Short answer: A calorie deficit means eating less than you burn. Roughly 7,700 kcal of total deficit equals 1 kg of fat. A 500 kcal daily deficit works out to about 0.5 kg a week. The calculator below takes your goal weight and timeframe and tells you the daily deficit required — and whether that rate is safe.
- Daily deficit needed (kcal) —
- Weekly loss (kg) —
- Maintenance calories (TDEE) —
This result is an estimate based on published formulas and is not medical advice.
Fill in the fields above to see your result. Everything updates automatically as you change the values.
How is a calorie deficit calculated?
Three steps. First, find your maintenance calories (TDEE). Second, multiply the weight you want to lose by 7,700 — that is your total deficit. Third, divide that total by the number of days in your timeframe.
Example: someone going from 78 kg to 70 kg has 8 kg to lose. Total deficit is 8 × 7,700 = 61,600 kcal. Over 16 weeks (112 days) that is a daily deficit of 550 kcal. If their TDEE is 2,300, their daily target is 1,750 kcal.
The 7,700 figure is an average; some of the weight lost is water and a little is muscle, so real results vary between people.
How fast is safe?
The general guidance is 0.5% to 1% of body weight per week. For someone at 80 kg that is 0.4-0.8 kg. Going faster is possible but costs something: more muscle loss, hunger and fatigue that are harder to manage, and a higher chance of quitting.
There is a floor too: below 1,200 kcal a day for women or 1,500 for men is not recommended. The calculator warns you when your target drops under that line — because the answer is not to eat less, it is to extend the timeframe.
I am in a deficit but not losing weight
There is almost always one of three explanations.
Intake is higher than assumed. Cooking oil, sauces, drinks and "just a bite" usually go uncounted. Portion estimates run 20-30% low on average.
Expenditure is lower than assumed. The activity level was set too high, which alone inflates the target by 300-500 kcal. In a deficit the body also reduces spontaneous daily movement.
Water retention is hiding fat loss. Salt, carbohydrates, the menstrual cycle and newly started exercise can hold several kilos of water. Judge the scale by a weekly average, not a single reading.
Example figures
The daily deficit required for a given amount of weight over a given timeframe. Cells marked ⚠ exceed 1,000 kcal a day — a pace that is not sustainable for most people.
| Weight to lose | 8 weeks | 12 weeks | 16 weeks | 24 weeks |
|---|---|---|---|---|
| 4 kg | 550 | 367 | 275 | 183 |
| 6 kg | 825 | 550 | 413 | 275 |
| 8 kg | ⚠ 1,100 | 733 | 550 | 367 |
| 10 kg | ⚠ 1,375 | 917 | 688 | 458 |
| 15 kg | ⚠ 2,063 | ⚠ 1,375 | ⚠ 1,031 | 688 |
This table shows example profiles, not your own result. Enter your details in the calculator above to get yours. Figures come from the Mifflin-St Jeor equation and are estimates.
Frequently asked questions
How big should my daily calorie deficit be?
For most people 300-500 kcal a day is ideal, giving roughly 0.3-0.5 kg per week. Larger deficits work faster but increase muscle loss and the odds of quitting.
How many calories are in 1 kg of fat?
Roughly 7,700 kcal. It is an average — part of any weight lost is water and a little is muscle, so results vary in practice.
How do I avoid losing muscle in a deficit?
Three things work: keep the deficit moderate (under 500 kcal a day), eat 1.6-2.2 g of protein per kg of body weight, and do resistance training. Together they push most of the loss towards fat.
Can I lose more than 1 kg a week?
People carrying a lot of weight often can at the start, and it is usually safe. As you approach your goal weight that pace becomes unsustainable and muscle loss becomes a real risk. The calculator flags it when you cross that line.
What if I go over at weekends?
A deficit works on a weekly average, not a daily one. A 500 kcal deficit on weekdays undone by 700 kcal extra at weekends erases your weekly deficit. One day does not matter; a regular weekend pattern can stop progress entirely.
When should I recalculate my deficit?
After every 3-4 kg lost. As your weight drops so does your TDEE, so the same intake no longer produces the same deficit. Sticking to the original number is the most common cause of a plateau.
Sources
- Mifflin MD, St Jeor ST et al. — A new predictive equation for resting energy expenditure in healthy individuals (1990)
- National Academies of Sciences — Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Protein and Amino Acids (2005)
- World Health Organization — Healthy diet
- USDA FoodData Central — Food composition database
Last updated: · This tool is for general information only. Consult a doctor or registered dietitian if you are pregnant, breastfeeding, managing a chronic condition or taking medication.