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These estimates are based on the Mifflin-St Jeor equation and standard energy-to-weight conversions (≈3,500 kcal per lb, ≈7,700 kcal per kg). Individual weight loss varies. This calculator is for general informational purposes and is not medical advice.
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How does a calorie deficit work?
Your body needs a certain number of calories a day to maintain its current weight — your maintenance calories (TDEE). A calorie deficit means eating below that number, so your body draws on stored energy, mostly fat, to make up the gap. This calculator estimates your TDEE via the Mifflin-St Jeor equation, then subtracts your chosen deficit to give a daily calorie target.
How large should my deficit be?
250 kcal/day is a gentle, easy-to-sustain deficit suited to slow, steady loss. 500 kcal/day is the most common recommendation — roughly 1 lb (0.45 kg) per week — balancing pace with sustainability. 750 kcal/day moves faster but is harder to stick to and more likely to push your target uncomfortably low, especially at lower maintenance levels. There's no universally "right" size — the deficit you can actually sustain matters more than the fastest one on paper.
How much weight can I lose with a 500 calorie deficit?
A 500 kcal/day deficit totals about 3,500 kcal/week — roughly 1 lb (about 0.45 kg) per week, based on standard energy-to-weight estimates (≈3,500 kcal ≈ 1 lb, ≈7,700 kcal ≈ 1 kg). This is a population-average estimate, not a guarantee for any individual week.
Maintenance calories vs. calorie deficit
Maintenance calories (from the calorie calculator) tell you what keeps your weight stable. A calorie deficit is how far below that number you deliberately eat to lose weight. If you also want a breakdown of protein, carbs, and fat within your deficit target, the macro calculator extends this further.
Why actual weight loss may differ from the estimate
The 3,500 kcal/lb rule is a simplified average — real results are affected by water retention, muscle vs. fat loss ratio, metabolic adaptation over time, and how consistently the deficit is actually maintained day to day. Use the estimate as a starting point and adjust based on your own real-world progress over a few weeks, not a single day.
Frequently asked questions
A calorie deficit means eating fewer calories than your body burns in a day, so it draws on stored energy — mostly body fat — to make up the difference. It's the basis of most weight-loss approaches.
First estimate your maintenance calories (TDEE) using your BMR and activity level. Then subtract your chosen deficit — commonly 250, 500, or 750 kcal/day — to get your daily calorie target for weight loss.
Yes, a 500 kcal/day deficit is one of the most commonly recommended starting points — it targets roughly 1 lb (about 0.45 kg) of weight loss per week and is usually sustainable for most people without being overly aggressive.
A 500 kcal/day deficit works out to about 3,500 kcal/week, which is roughly equivalent to 1 lb (about 0.45 kg) of weight loss per week, based on standard energy-to-weight estimates. Actual results vary by individual.
A 750 kcal/day deficit is larger and can be harder to sustain, and it increases the risk of your calorie target dropping too low, especially if your maintenance calories are already modest. It can work for some people short-term but a smaller, steadier deficit is often easier to maintain.
Yes. Very large deficits can push your daily calories dangerously low, which can affect energy, muscle mass, and long-term adherence. This calculator shows a visible warning and caps the displayed target if your selected deficit would result in an unusually low calorie target.
It gives a solid, evidence-informed estimate, not a guarantee. Actual weight loss depends on individual metabolism, body composition, adherence, and other factors a formula can't fully capture — treat the result as a starting point to test and adjust.
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These estimates are based on the Mifflin-St Jeor equation and standard energy-to-weight conversions. Individual weight loss and calorie needs can vary. This calculator is for general informational purposes and is not medical advice. Consult a qualified healthcare professional before making major dietary changes.