Calorie Deficit Calculator
Pick how fast you want to lose weight and get an estimated daily calorie target – plus the macro split. Results are estimates, not medical advice; talk to a doctor before starting a diet.
Fill in your details and your plan appears here instantly.
Your weight-loss plan
Macros at your target
How a calorie deficit works
One pound of body fat stores roughly 3,500 kcal. To lose a pound a week you therefore need a deficit of about 500 kcal per day – either by eating less, moving more, or both. This calculator starts from your maintenance calories (your TDEE) and subtracts the deficit that matches the pace you choose.
How big should your deficit be?
Research and coaching practice converge on 15-25% below maintenance for most people – typically 300-750 kcal a day. Larger deficits move the scale faster but cost you muscle, training quality and adherence. Leaner people should use smaller deficits; people with more to lose can tolerate larger ones.
Protecting muscle while you cut
Two levers matter most: keep protein high (around 1 g per pound of body weight, which this calculator uses) and keep resistance training in your week. Together they tell your body to burn fat rather than muscle when calories are low.
Choosing your pace
The pace selector above offers four speeds: losing 0.5, 1, 1.5 or 2 lb per week. Each pound a week corresponds to a nominal daily deficit of roughly 500 kcal, so the four options work out to gaps of about 250, 500, 750 and 1,000 kcal a day. Those are the figures the calculator starts from. It will not set a daily target below its built-in limits, so the deficit you actually get can be smaller than the one you picked, and real-world loss varies from week to week.
The NHS suggests aiming to lose 0.5 to 1 kg (about 1 to 2 lb) a week at a steady rate. If you are unsure where to start, 1 lb a week is a reasonable middle: quick enough to see, slow enough to live with. You can change pace at any time by rerunning the calculator.
Why the scale can lag behind the maths
The 3,500 kcal rule treats the body like a static machine, and real bodies adapt. As you get lighter, your maintenance calories fall with you, so a fixed daily gap buys less loss over time. A widely cited analysis by researcher Kevin Hall showed that the simple rule of thumb tends to overestimate how much weight a given deficit will shift.
The answer is not a bigger deficit. Recalculate your numbers every 10 lb or so of loss, judge progress on weekly averages rather than single weigh-ins, and give any new target a few weeks before adjusting again.
Frequently asked questions
Why has my weight loss stalled after a few weeks?
As you get lighter your TDEE drops, so a deficit that worked at 200 lb may be maintenance at 180 lb. Recalculate every 10 lb lost, and double-check portions – small tracking creep is the most common stall cause.
Is a 1,000 kcal daily deficit safe?
Only for people with a large amount of weight to lose, and ideally with medical guidance. For most people it costs muscle and rebounds. This calculator caps targets at 1,200 kcal (women) / 1,500 kcal (men) per day.
Should I create the deficit with diet or exercise?
Mostly diet, supported by activity. It is far easier to skip 500 kcal than to burn it – but keeping daily steps and training up protects muscle and gives you more food to work with.
Do I need to hit the target exactly every day?
No – weekly averages are what count. Eating slightly more on training days and slightly less on rest days works just as well as a flat daily number.
How long should I stay in a calorie deficit?
A deficit is a tool for a period of time, not a permanent way of eating. Once you reach your goal, recalculate your maintenance calories at your new weight and move back up to that level. For a long or aggressive cut, checking in with a doctor or registered dietitian along the way is a sensible step.
Does this calculator use metric or imperial units?
Both. Use the Units toggle at the top of the calculator to switch between imperial (feet/inches and pounds) and metric (centimetres and kilograms). Your targets are shown in calories either way.
Disclaimer
This calculator gives estimates for general information only, not medical advice. Speak to a doctor or registered dietitian before starting a weight-loss plan if you are pregnant, under 18, managing a condition such as diabetes, or planning a large or fast loss.