Calorie Deficit Calculator

A calorie deficit means eating fewer calories than your body burns in a day. When you are in a deficit, your body makes up the difference from stored energy (mostly body fat) and you lose weight over time.

A moderate deficit of about 15–25% below your maintenance calories (TDEE) is a sustainable default. Larger deficits lose weight faster but are harder to stick to and risk muscle loss. This calculator uses roughly a 20% deficit and never recommends going below safe calorie floors.

It depends on your deficit and starting point. This calculator projects a realistic date using a dynamic model that accounts for how your metabolism and body composition change as you lose weight: a more honest estimate than the old, fixed '3,500 calories = 1 pound' rule.

The flat 3,500-calorie rule assumes your energy expenditure never changes. For most people our projection is slower, because as you get lighter you burn fewer calories, so weight loss gradually slows and can plateau. If you are already lean it can go the other way: you lose a mix of fat and muscle that holds less energy per kilo than fat alone, so you may lose noticeably faster at first before it slows down. Either way, modelling your body composition and metabolism is more honest than a single fixed linear estimate.

As a general safety floor, this tool will not recommend dropping below about 1,500 kcal/day for men or 1,200 kcal/day for women. Very low intakes should only happen under professional supervision.

You can preserve most muscle by keeping a moderate deficit, eating enough protein (around 1.6–2.2 g per kg of bodyweight), and doing resistance training. Crash diets with very low calories and no training are the main cause of muscle loss.

No. Treat the number as a well-informed starting target. Track your weight trend over 2–3 weeks and adjust: if the scale is not moving on average, lower intake slightly or move more.

It depends mainly on your deficit size and starting weight. As a rough guide, one kilo of fat holds about 7,700 kcal, so a steady deficit of around 500 kcal/day points to roughly 5 months for 10 kg. In practice it usually takes a little longer, because our dynamic model accounts for your metabolism slowing as you get lighter. Enter your goal weight above for a personalised timeline.

A 1,000 kcal/day deficit is aggressive and only sensible for some people with a higher starting weight, ideally with guidance. The risk is dropping below the safe calorie floors (about 1,500 kcal for men and 1,200 kcal for women), losing muscle, and struggling to keep it up. For most people a deficit of about 15–25% below maintenance is more realistic and easier to sustain.

Neither figure is a goal: 1,200 kcal (women) and 1,500 kcal (men) are the safety floors we never recommend going under, so they only really fit the smallest, least active people. Most people should eat noticeably more and still lose fat steadily. Instead of choosing a round number, enter your details above so the calculator sets a target from your own maintenance calories.

A common, sustainable rate is about 0.5–1% of your bodyweight per week, which works out near 2–4 kg per month for many people. Heavier starting points often lose faster at first, while leaner bodies lose more slowly. Faster is not better: pushing harder mostly costs muscle and makes the diet harder to maintain.

No. This calculator is for general information and education only and is not medical or nutritional advice. Consult a qualified professional before changing your diet, especially if you are pregnant, have a history of disordered eating, or have a medical condition.