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Calorie Deficit Calculator
A calorie deficit — eating less energy than you burn — is the mechanism behind every diet that has ever worked, whatever its branding. This calorie deficit calculator sizes yours: it estimates the calories you burn, subtracts a sustainable amount, and shows the projected rate of loss with every step of the math visible.
Your Facts
Fill in the form and press Calculate — your personal label prints here.
The physics is settled; the craft is in the size. Too small a deficit and progress hides inside daily weight noise. Too large and hunger, fatigue, muscle loss, and rebound eating dismantle the plan by week six. The calculator defaults to the evidence-backed sweet spot: 250–500 kcal below maintenance.
Enter your details below — your results label shows maintenance first, then the deficit targets, so you always see what you're subtracting from.
How big should a calorie deficit be?
A 500 kcal daily deficit produces roughly 0.5 kg (1 lb) of loss per week for most people — the pace guidelines from major health bodies converge on, fast enough to see, slow enough to keep your muscle and your temper. A 250 kcal deficit halves the pace but barely registers as restriction, which makes it the better choice for lighter people, first-timers, and anyone who has rebounded from aggressive diets before.
Deficits beyond 750–1,000 kcal belong under professional supervision. The research on very-low-calorie diets is clear about the trade: faster initial loss, but proportionally more muscle lost, larger metabolic adaptation, and worse long-term maintenance. If a deadline tempts you toward aggression, a better lever is protein and strength training, which shift what the lost weight is made of.
Why the scale lies for the first two weeks
Start a deficit and the scale often drops fast — then stalls, panicking everyone. Both movements are mostly water. Early on, you deplete glycogen, which is stored with about 3 g of water per gram; that's the fast 'loss.' Then sodium shifts, training stress, and (for women) cycle timing can hold water and mask genuine fat loss for two to four weeks.
The defense is measurement discipline: weigh under identical conditions (morning, after the bathroom, before food), compare weekly averages rather than days, and give any deficit at least two full weeks before adjusting. A trend line can't be spooked by a salty dinner; a single Tuesday weigh-in can.
Holding a deficit without living hungry
The deficits that survive contact with real life share a shape: high protein (1.6–2.2 g/kg — it's the most satiating macro), high food volume (vegetables, fruit, soups, potatoes deliver fullness per calorie), and most of the cutting done where you won't miss it — liquid calories, cooking oil, and mindless snacks routinely hide 300–500 kcal.
Structure beats willpower: a diet break at maintenance every 8–12 weeks, one flexible meal a week planned rather than 'cheated,' and the target framed as a weekly budget so social life fits inside the plan instead of colliding with it.
Frequently asked questions
A calorie deficit means consuming fewer calories than your body burns, forcing it to draw the difference from stored energy — mostly body fat. It's created by eating less, moving more, or both, and it is the underlying mechanism of every effective weight-loss diet.
For most people, yes — 500 kcal below maintenance yields about 0.5 kg (1 lb) of loss per week and is the most commonly recommended pace. Smaller or lighter people often do better at 250–350 kcal, since 500 can be too large a share of their total burn.
The scale trend is the only honest referee: if your weekly average weight falls over 2–4 weeks, you're in a deficit; if it doesn't, you aren't — regardless of what any calculator says. Calculators estimate your starting point; your logged results calibrate it.
Usually one of four things: portions are larger than logged (the most common), activity level was overestimated, water retention is masking fat loss (normal for 2–4 weeks), or weekend intake erases weekday deficits. Tighten tracking for two weeks and judge the weekly average before concluding anything about your metabolism.