Calorie Deficit Calculator
Calorie Deficit Calculator
A calorie deficit is the daily gap between what you burn and what you eat. Pick how much weight you want to lose and how long you've got. We'll tell you the deficit needed, flag whether it's safe, and split it between cutting food and adding exercise.
Last updated: May 1, 2026
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Daily deficit needed
Enter your TDEE, target loss, and timeline.
Eat
-- kcal/day
less from food
Burn
-- kcal/day
more from exercise
New daily intake target
-- kcal/day
Tools that help you stay in deficit
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Compare deficit levels
Three deficit aggressiveness levels for the same target loss. Faster isn't always better.
| Level | Deficit | Weekly loss | Timeline | Best for |
|---|---|---|---|---|
| Mild (10% TDEE) | -- | -- | -- | Final cut, recomp, easy adherence |
| Moderate (20% TDEE) | -- | -- | -- | Standard fat loss, balanced |
| Aggressive (25% TDEE) | -- | -- | -- | Deadline-driven cuts, short phases only |
How this calculator works
The 7,700 kcal per kg rule
One kilogram of body fat stores roughly 7,700 kcal of energy (about 3,500 kcal per pound). Burn that gap over time and you lose the weight. Wishnofsky proposed this in 1958, and it remains a useful planning estimate even though real fat loss is messier.
Why percentage of TDEE matters more than absolute kcal
A 500 kcal daily deficit is moderate (20%) for someone burning 2,500 kcal per day. The same 500 kcal is aggressive (25%) for someone burning 2,000 kcal. The body's response to a deficit scales with metabolic rate, not absolute calories. We grade safety as a percentage of your TDEE, not as a fixed number.
Diet vs exercise tradeoffs
Diet is more reliable: cutting 500 kcal from food is easier and more predictable than burning 500 kcal through exercise. Exercise, especially resistance training, preserves lean muscle during a deficit and raises your TDEE. A common rule of thumb: 70% of the deficit from food, 30% from added activity.
Limitations
- Linear weight loss is a planning fiction. Real loss includes water, glycogen, and varies week to week.
- Metabolic adaptation slows fat loss after 8 to 12 weeks of continuous deficit.
- The 7,700 kcal per kg rule overestimates loss long-term: actual values land closer to 7,000 to 7,500.
- Hormones, sleep, and stress all affect the result and are not modeled here.
Sources
- Wishnofsky M. Caloric equivalents of gained or lost weight. American Journal of Clinical Nutrition. 1958;6(5):542-546.
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet. 2011;378(9793):826-837.
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation. Journal of the International Society of Sports Nutrition. 2014;11:20.
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Frequently asked questions
What is a safe daily calorie deficit?
A safe daily calorie deficit is typically 10-20% of your TDEE (total daily energy expenditure). For most adults, this means 250-500 kcal per day. Going above 25% risks muscle loss, hormonal disruption, and rebound weight gain. The lower end works best for sustainable long-term progress.
How many calories should I cut to lose 1 pound a week?
One pound of fat equals approximately 3,500 kcal, so a daily deficit of 500 kcal will produce about one pound of loss per week. For 1 kilogram per week, you need a daily deficit of about 1,100 kcal, which is aggressive for most people. Slower loss is more sustainable and protects muscle.
Can I lose weight without exercise?
Yes. Weight loss is primarily about energy balance, so cutting calories alone will produce fat loss. However, exercise preserves lean muscle during a deficit and improves cardiovascular and metabolic health. Combining diet and exercise produces better body composition outcomes than diet alone.
Is a 1000 calorie deficit too much?
For most adults with a TDEE under 4000 kcal, a 1000 kcal daily deficit exceeds 25% of total burn and is considered too aggressive. It typically causes muscle loss, hormonal issues, fatigue, and high relapse rates. Athletes and very large individuals may tolerate it short-term, but not as a default approach.
How long should I stay in a calorie deficit?
Most evidence supports 8-12 week deficit phases followed by a maintenance break of 2-4 weeks. Continuous deficit beyond 16 weeks causes metabolic adaptation, where your body burns less energy than calculated. Periodic breaks restore hormonal balance and improve long-term adherence.
Does the 7700 kcal per kg rule actually work?
It is a useful planning estimate but not a precise rule. The original 1958 Wishnofsky calculation assumed 100% fat loss with no metabolic adaptation, which is unrealistic. Real-world fat loss is closer to 7,000-7,700 kcal per kg, varies between individuals, and slows over time as the body adapts.
Should I create a deficit through diet or exercise?
A combination works best. Diet is more reliable because creating a 500 kcal deficit through eating less is easier than burning 500 kcal through exercise. Exercise preserves muscle, improves health, and increases the ceiling of how much you can eat. A 70% diet, 30% exercise split is a common starting point. A food scale is the single highest-ROI tool for diet-side accuracy: most people underestimate intake by 20-30% without one. See food scales on Amazon.
What happens if my deficit is too aggressive?
An overly aggressive deficit (above 25% of TDEE) typically causes loss of muscle mass alongside fat, lowered testosterone or estrogen, fatigue, hunger that becomes hard to manage, and high relapse rates. The faster you lose weight, the more likely you are to regain it. Slower loss preserves the result.
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