Calorie Deficit Calculator: How Many Calories Should You Cut?

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.

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.

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.