Calorie Deficit Calculator: How Many Calories Should You Cut?
Estimates only. Consult a healthcare professional before major dietary changes.
📊 Methodology: This calculator uses validated clinical formulas as cited in the sources below. Results are estimates for general informational purposes. Consult a qualified healthcare professional before making health decisions.
Health disclaimer: This calculator provides estimates for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Results are based on population averages and may not apply to individuals with specific health conditions. Always consult a qualified healthcare professional. Reviewed by Dr. P Nair, MBBS, MD.
What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body burns in a day. Your body requires a certain number of calories to maintain its current weight — this is your Total Daily Energy Expenditure (TDEE). When you eat less than your TDEE, your body draws on stored fat to make up the difference, resulting in fat loss over time. Need to continue this calculation? Try the TDEE Calculator or the Calorie Calculator.
The size of your deficit determines how quickly you lose weight. A 500-calorie daily deficit produces approximately 0.5 kg of fat loss per week — since roughly 7,700 calories of deficit equals one kilogram of fat. This is the most widely recommended deficit rate because it is sustainable without sacrificing muscle mass or significant amounts of energy.
How to use this calculator
- Enter your age, sex, weight, and height — these inputs determine your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, the most validated formula for adults.
- Select your activity level — be honest here. Most desk workers are sedentary or lightly active, even if they exercise 3 times per week.
- Choose your weekly weight loss goal — 0.5 kg/week is the recommended starting point for most people.
- Read your results — the calculator shows your maintenance calories (TDEE), your daily calorie target, and your projected loss over 4 weeks.
How big should your calorie deficit be?
The right deficit size depends on your starting weight, lifestyle, and how quickly you want to lose weight:
- 250–500 calories/day (0.25–0.5 kg/week): The gentlest, most sustainable approach. Recommended for people close to their goal weight or new to dieting. Muscle loss is minimal at this rate.
- 500–750 calories/day (0.5–0.75 kg/week): The most commonly recommended range. Fast enough to see clear progress, sustainable enough to maintain for months. Works well for most adults.
- 750–1,000 calories/day (0.75–1 kg/week): Appropriate for people with higher starting body weight. Requires careful attention to protein intake (1.8–2.2 g/kg) to preserve muscle mass.
- Below 1,200 calories/day (women) or 1,500 calories/day (men): Not recommended without medical supervision. Deficits this large increase muscle loss, cause nutrient deficiencies, and often trigger metabolic adaptation — where the body reduces its energy expenditure in response to restriction, making continued loss harder.
Crash diets that cut calories severely cause rapid initial weight loss — mostly water and glycogen, not fat — followed by stalled progress as the body adapts. A moderate, consistent deficit outperforms aggressive restriction over any meaningful timeframe.
Calorie deficit vs maintenance calories — what is the difference?
Your maintenance calories (TDEE) is the number of calories at which your weight stays stable. Eat above this and you gain weight; eat below it and you lose weight. Your calorie deficit is the gap between your TDEE and your daily intake. If your TDEE is 2,400 and you eat 1,900 calories, your daily deficit is 500 calories.
TDEE is not a fixed number — it decreases as you lose weight, because a lighter body requires less energy to function. This is why weight loss often slows after the first few weeks even at the same calorie intake. Recalculate your TDEE every 4–6 weeks during a fat loss phase and adjust your intake accordingly.
Tips to sustain a calorie deficit without feeling hungry
- Prioritise protein (1.6–2.2 g per kg of body weight): Protein is the most satiating macronutrient and has the highest thermic effect — approximately 25–30% of protein calories are burned in digestion. High protein intake also preserves muscle during a deficit.
- Eat high-volume, low-calorie foods: Vegetables, fruits, lean proteins, and broth-based soups add bulk and satiety without many calories. 500g of cucumber is under 80 calories.
- Include dietary fibre (25–35 g/day): Fibre slows digestion, stabilises blood sugar, and increases satiety. Vegetables, legumes, oats, and whole grains are good sources.
- Space meals to control hunger: Eating 3–4 meals with protein at each sitting is more effective for hunger control than skipping meals and eating one large portion.
- Stay hydrated: Thirst is often mistaken for hunger. Drinking water before meals reduces calorie intake at that meal in controlled studies.
- Track intake for at least 4–6 weeks: Studies consistently show people underestimate their calorie intake by 20–40%. Tracking removes guesswork and reveals where hidden calories come from.
Safe calorie deficit ranges by goal
Very slow (200–300 kcal deficit): best for athletes preserving muscle during a cut. Standard fat loss (400–600 kcal): produces 0.5 kg/week loss, the recommended rate for most adults. Faster loss (700–1,000 kcal): appropriate for those with significant weight to lose; add extra protein. Aggressive (above 1,000 kcal): only under medical supervision — risks muscle loss, nutrient deficiency, and metabolic adaptation.
Why a deficit that's too large backfires
When you cut too many calories, your body responds by: (1) Reducing BMR by 10–20% through metabolic adaptation — making the deficit smaller than intended. (2) Breaking down muscle for energy — reducing long-term metabolic rate. (3) Triggering intense hunger hormones (ghrelin spike) that make the deficit unsustainable. Research shows slow, moderate deficits lose the same total fat as aggressive ones while preserving more muscle and being far more sustainable.
How long will it take to reach your goal weight?
Weeks to goal = (Current weight − Goal weight in kg) × 7,700 kcal ÷ Daily deficit. At a 500 kcal/day deficit: 10 kg loss takes approximately 154 days (22 weeks). However, real weight loss includes plateaus every 4–6 weeks as the body adapts. Plan for 20–30% longer than the pure calculation suggests, and include 1–2 diet breaks (returning to maintenance calories for 1–2 weeks) during longer cuts.
Safe calorie deficit range: avoiding muscle loss and metabolic slowdown
A 300–500 kcal/day deficit is optimal for most people: enough to produce meaningful fat loss (0.3–0.45 kg/week) without triggering significant muscle loss or metabolic adaptation. Deficits above 750 kcal/day increase cortisol, suppress thyroid function, and cause disproportionate muscle loss — you lose weight but become "skinny fat." The minimum effective deficit is 200 kcal/day (0.2 kg/week fat loss); the maximum recommended is 750 kcal/day.
Zigzag calorie cycling: beating the metabolic plateau
Metabolic adaptation (your TDEE decreasing as you lose weight) can stall fat loss after 8–12 weeks. Zigzag calorie cycling combats this by alternating high-calorie days (at TDEE) and low-calorie days (TDEE minus 700+). Example: 5 days at TDEE −500 kcal, 2 days at TDEE +200 kcal. Weekly average is still a 430 kcal/day deficit. The high-calorie days restore leptin levels and give a psychological break from restriction.
Further reading: walking weight loss guide
Frequently asked questions about calorie deficit
How do I calculate my calorie deficit? Your daily deficit = TDEE – daily calorie intake. Calculate TDEE using the Mifflin-St Jeor equation multiplied by your activity factor. Subtract your planned daily intake from this number. A 500-calorie deficit produces approximately 0.5 kg of fat loss per week (since 7,700 calories ≈ 1 kg of fat).
Is a 500-calorie deficit safe every day? Yes, for most healthy adults. A 500-calorie daily deficit produces approximately 0.5 kg per week of fat loss — a rate supported by most nutrition organisations as safe and sustainable. It is large enough to produce visible progress while preserving muscle and energy levels.
How long to lose 5 kg on a calorie deficit? At a 500-calorie daily deficit (0.5 kg/week), losing 5 kg takes approximately 10 weeks. At 750 calories/day deficit (0.75 kg/week), approximately 7 weeks. Results vary based on starting weight, adherence, and whether the TDEE estimate is accurate.
What if I am not losing weight despite a deficit? The most common cause is underestimating calorie intake — weigh and measure food rather than estimating. Also recalculate TDEE with your current (lower) weight, as a lighter body burns fewer calories. Water retention from hormonal changes, high sodium, or starting a new exercise programme can also mask fat loss on the scale.
Can I eat anything in a calorie deficit and still lose weight? In terms of fat loss — yes. A calorie deficit causes fat loss regardless of food composition. However, food quality significantly affects satiety, muscle preservation, nutrient adequacy, and how sustainable the deficit is. High-protein, high-fibre diets are substantially easier to maintain than calorie-equivalent low-protein diets.
Useful sources
- NIH — Weight Management Guidelines
- WHO — Obesity and Overweight Fact Sheet
- Mifflin MD et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 51(2):241–247.
Sources & References
- Hall KD et al. — Energy Balance and Body Weight (NIH) — 3,500-kcal/lb approximation and its limitations; dynamic energy balance model
- Academy of Nutrition and Dietetics — Weight Management — Safe deficit ranges (500–750 kcal/day) and minimum intake floors
Calorie deficit and expected weight loss
| Daily Deficit | Weekly Deficit | Weekly Fat Loss | Monthly Fat Loss |
|---|---|---|---|
| 250 kcal/day | 1,750 kcal | ~0.25 kg (0.55 lb) | ~1 kg (2.2 lb) |
| 500 kcal/day | 3,500 kcal | ~0.45 kg (1 lb) | ~2 kg (4.4 lb) |
| 750 kcal/day | 5,250 kcal | ~0.68 kg (1.5 lb) | ~3 kg (6.6 lb) |
| 1,000 kcal/day | 7,000 kcal | ~0.9 kg (2 lb) | ~4 kg (8.8 lb) |
Note: 1 kg of body fat = approximately 7,700 kcal. However, real-world weight loss is rarely linear — water retention, metabolic adaptation, and muscle changes affect the scale day to day.
Safe deficit ranges by goal
| Goal | Daily Deficit | Who It Suits |
|---|---|---|
| Very slow / sustainable | 200–300 kcal | Athletes preserving muscle; slow recomposition |
| Standard fat loss | 400–600 kcal | Most people; minimal muscle loss risk |
| Faster fat loss | 700–1,000 kcal | Those with significant weight to lose; add protein |
| Very fast (not recommended) | 1,000+ kcal | Only under medical supervision |