📉 Calorie Deficit Calculator — Find Your Fat Loss Calorie Target
Enter your goal weight and preferred weekly loss rate to calculate your daily calorie target, projected timeline, and safe deficit range.
Weekly total deficit
Quick Deficit Facts
Sources: NIH, NIDDK, Dietary Guidelines for Americans
How a Calorie Deficit Creates Fat Loss: The Science Explained
Fat cells store energy in the form of triglycerides. When your calorie intake is lower than your total daily expenditure, your body draws on these stores to fuel its functions. One kilogram of body fat contains approximately 7,700 calories of stored energy.
This calculator uses the Mifflin-St Jeor equation — considered more accurate than the original Harris-Benedict formula — to estimate your TDEE:
Female: (10 × kg) + (6.25 × cm) − (5 × age) − 161
Your weekly loss target converts to a daily calorie deficit: 0.5 kg/week = 3,850 ÷ 7 = 550 cal/day. The calculator subtracts this from your TDEE to find your daily calorie target.
Safe deficit ranges
Calorie Deficit: Weekly Loss Rate Reference
How calorie deficits translate to fat loss over time. Based on 7,700 cal per kg of fat.
| Daily Deficit | Weekly Loss | Monthly Loss | 10 kg in… | Safety Rating |
|---|---|---|---|---|
| 250 cal | 0.23 kg | ~1 kg | ~43 wks | ✅ Very Safe |
| 500 cal | 0.45 kg | ~2 kg | ~22 wks | ✅ Recommended |
| 750 cal | 0.68 kg | ~3 kg | ~15 wks | ⚠️ Moderate |
| 1,000 cal | 0.91 kg | ~4 kg | ~11 wks | ⚠️ High Risk |
| 1,500 cal | 1.36 kg | ~6 kg | ~7 wks | ❌ Not Advised |
Frequently Asked Questions
Calorie Deficit Calculator for Women — Safe Minimums and Muscle Preservation
Women face a specific challenge when creating a calorie deficit: the 1,200-calorie minimum is low enough that many women in a deficit are eating within 200–300 calories of it, leaving almost no margin for adjustments when progress stalls. This is why many nutrition researchers argue that women are better served by increasing activity to create part of their deficit rather than restricting food intake to the minimum.
Women also experience calorie need fluctuations across the menstrual cycle of approximately 100–300 calories, peaking in the luteal phase (days 15–28). Rigidly maintaining the same daily target throughout the month can feel significantly harder in the second half of the cycle — and this is physiological, not a willpower failure. Some practitioners recommend slightly relaxing the deficit in the luteal phase and compensating in the follicular phase, which tends to have lower hunger and higher energy for exercise.
How Long to Lose 10kg in a Calorie Deficit?
At the recommended 0.5 kg per week loss rate, losing 10 kg takes approximately 20 weeks (5 months). This assumes the deficit is maintained consistently, which research shows is the primary variable — not the size of the deficit. A person maintaining a 400-calorie deficit for 20 weeks will achieve better results than someone who maintains a 700-calorie deficit for 8 weeks before giving up.
It is also worth noting that scale weight rarely drops linearly. Water retention from increased exercise, hormonal fluctuations, dietary sodium, and muscle glycogen storage can mask fat loss for 1–3 weeks at a time. Tracking a 4-week rolling average of body weight, alongside progress photos and measurements, gives a more accurate picture of genuine fat loss progress than daily weigh-ins.
Calorie Deficit vs. Exercise: Which Burns More Fat?
Diet creates a far larger calorie deficit than exercise for most people. A 60-minute moderate jog burns approximately 400–600 calories — roughly equivalent to a single missed snack. Exercise is excellent for health, cardiovascular fitness, muscle preservation during a cut, and metabolic health, but it is a poor primary tool for creating a calorie deficit because it also increases appetite proportionally.
The most effective approach combines a dietary deficit of 300–500 calories with 3–5 hours per week of exercise (2–3 resistance training sessions and 2–3 cardio sessions). This approach creates the deficit primarily through food, while exercise preserves or builds muscle, improves insulin sensitivity, and provides health benefits that dietary restriction alone cannot deliver.
Understanding Calorie Deficits: Beyond Simple Arithmetic
The "3,500 calories = 1 lb of fat" rule is a useful approximation but not a precise prediction. As you lose weight, your TDEE decreases because you are moving a lighter body and your body down-regulates energy expenditure through adaptive thermogenesis. This means the same 500-calorie deficit produces less loss over time — a phenomenon that explains why weight loss always slows as you approach your goal.
Diet Breaks and Refeed Days
Periodic diet breaks — one to two weeks eating at TDEE maintenance after 6–8 weeks of deficit — have been shown in research to partially reverse adaptive thermogenesis and improve adherence. Refeed days (eating at maintenance for 1–2 days per week) have a smaller but real effect. Both strategies can improve long-term results by giving the body periodic recovery from the metabolic stress of sustained restriction.
Body Recomposition: Losing Fat While Building Muscle
True body recomposition — simultaneously losing fat and gaining muscle — is possible but mainly occurs in specific circumstances: beginners who have never trained, people returning after a long break, individuals with significant excess body fat, and those using certain performance-enhancing substances. For most trained individuals, dedicated cut and bulk phases produce better body composition outcomes than trying to achieve both simultaneously.
Disclaimer: This calculator provides estimates for informational purposes only and does not constitute medical or nutritional advice. Calorie needs vary significantly between individuals. Consult a registered dietitian or physician before undertaking a significant calorie deficit, especially if you have any medical conditions or a history of disordered eating.