Free Calorie Deficit Calculator
0.5 kg (~1 lb) per week
What is a calorie deficit?
A calorie deficit is the gap between the calories you eat and the calories you burn. Burn more than you eat and your body draws on stored energy to cover the shortfall — which is how fat loss happens. The size of that daily gap sets how fast you lose.
How big should your deficit be?
For most people, 300–500 calories per day is the sweet spot: fast enough to see progress, gentle enough to stick with and protect muscle. Very large deficits can leave you tired, hungry, and prone to rebound eating — so this calculator never drops below a safe minimum (1,200 kcal for women, 1,500 kcal for men).
Deficit size, rate of loss and timeline
Using the 7,700 kcal ≈ 1 kg approximation, here is what each deficit is worth per week, and how long it takes to shift 5 kg or 10 lb at that rate:
| Daily deficit | Per week | Loss / week | 5 kg takes | 10 lb takes |
|---|---|---|---|---|
| −250 kcal | −1,750 kcal | 0.2 kg (0.5 lb) | 22 weeks | 20 weeks |
| −500 kcal | −3,500 kcal | 0.5 kg (1 lb) | 11 weeks | 10 weeks |
| −750 kcal | −5,250 kcal | 0.7 kg (1.5 lb) | 7 weeks | 7 weeks |
| −1000 kcal | −7,000 kcal | 0.9 kg (2 lb) | 6 weeks | 5 weeks |
A deficit is easier to judge as a share of what you burn than as a raw number. Against a moderately active TDEE of about 2122 kcal (reference woman) and 2732 kcal (reference man), a 500 kcal cut is 24% and 18% respectively. Anything much past 20–25% of TDEE gets hard to hold, which is why smaller people generally need smaller absolute deficits rather than the same 500 kcal everyone quotes.
In this calculator the three paces map to fixed rates of change: 0.25 kg/week (mild), 0.5 kg/week (moderate) and 1 kg/week (aggressive). Whichever you pick, intake is floored at 1200 kcal for women and 1500 kcal for men — if the maths would go below that, the target is raised and the projected rate recalculated to match what you would actually be eating.
Where the 7,700-calorie rule breaks down
The rule assumes every calorie of deficit comes out of fat and that your expenditure stays constant. Neither holds exactly:
- Early loss is mostly not fat. The first week or two typically includes several pounds of glycogen and its associated water, which is why initial progress looks faster than the equation predicts.
- Expenditure falls as you shrink. A smaller body costs less to maintain and less to move, so a fixed intake becomes a smaller deficit over time. This is the main reason linear projections overshoot.
- Some loss is lean tissue. Larger deficits and low protein both increase that share. Resistance training and enough protein are the two levers that keep it small.
- Logging is imperfect. Self-reported intake is routinely under-estimated by a meaningful margin. If two weeks of careful logging shows no change, the honest explanation is usually the log, not metabolism.
None of this makes the arithmetic useless — it is still the best planning tool available. Treat the projection as a forecast to revise, not a schedule.
A realistic timeline
Enter a goal weight above and the calculator estimates how many weeks it should take at your chosen pace. Steady loss of 0.5–1% of body weight per week is a sensible, sustainable target. Slower is often better: it's easier to maintain and preserves more muscle.
Breaking through plateaus
- Recalculate as you shrink — a lighter body burns fewer calories, so update your target every few kilos.
- Don't panic over water weight — the scale bounces daily; watch the multi-week trend.
- Prioritise protein and strength training to keep muscle while losing fat.
- Audit the log before cutting further. Weigh cooking oil, count drinks, and log the bites taken while cooking. Reclaiming 200 kcal of under-reporting beats removing 200 kcal of food you were enjoying.
- Add movement instead of subtracting food when hunger is the binding constraint. A daily 30-minute walk is worth roughly 100–150 kcal for most people, and it does not compete with your appetite the way a smaller dinner does.
- Give it three weeks before concluding anything. Normal fluctuation in body water is larger than a week of fat loss, so shorter windows cannot distinguish a plateau from noise.
Eating well inside a deficit
The difficulty of a deficit depends far more on what you eat than on how large it is. Two food properties do most of the work:
- Protein is the most satiating macronutrient per calorie and protects lean mass while you lose fat. Set it first — see high-protein foods and the macro calculator.
- Energy density decides how much food your budget buys. At 0.3 kcal/g you can eat a kilo of food for 300 calories; at 5 kcal/g the same calories are 60 g. Building meals around low-calorie foods and high-fibre foods is what makes a deficit feel survivable.
Ready to act on your deficit? Track it for free in ourcalorie tracker, and look up any food's real numbers in the food database. This tool provides general information and is not medical advice — check with a professional before making significant changes.
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Calorie deficit FAQ
Is this calorie deficit calculator free?
Yes — 100% free, no sign-up, no ads. You get your target calories, daily deficit, and timeline instantly.
What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns in a day (your TDEE). When you do this consistently, your body uses stored energy — mostly fat — to make up the difference, and you lose weight.
How big should my calorie deficit be?
A deficit of about 300–500 calories per day is a sustainable sweet spot for most people, producing roughly 0.25–0.5 kg (0.5–1 lb) of loss per week. Larger deficits work faster but are harder to sustain and can cost muscle, so this calculator caps intake at a safe minimum.
How many calories is 1 kg or 1 lb of fat?
Roughly 7,700 calories per kilogram, or about 3,500 calories per pound. That is why a 500-calorie daily deficit (3,500/week) leads to about 1 lb of loss per week.
Why has my weight loss stalled?
As you lose weight your TDEE falls, so an old deficit becomes maintenance. Recalculate every few kilos, be patient through short-term water-weight plateaus, and adjust intake or activity if the trend flattens for several weeks.
How long will it take me to lose 5 kg or 10 lb?
At a 500 kcal daily deficit — about 0.5 kg (1 lb) a week — 5 kg takes roughly 11 weeks and 10 lb about 10 weeks. Halve the deficit to 250 kcal and those become 22 and 20 weeks. The full table is on this page.
What is the lowest number of calories I should eat?
This calculator will not recommend below 1200 kcal/day for women or 1500 kcal/day for men. Below those levels it becomes hard to meet micronutrient needs, lean-mass loss accelerates, and adherence collapses. Very-low-calorie diets exist but belong under medical supervision.
Is a bigger deficit better?
Only up to a point. Doubling a 500 kcal deficit to 1000 kcal roughly doubles weekly loss on paper — 0.5 kg becomes 0.9 kg — but hunger, fatigue, training quality and lean-mass loss all worsen faster than the rate improves. Most people lose more total fat over six months on the smaller deficit because they actually stick to it.
Should I take diet breaks or refeed days?
They are optional, not required. Eating at maintenance for a few days can help psychologically and restores training performance, but it also pauses fat loss for those days. If you use them, plan them rather than letting them happen — an unplanned high day can erase most of a week's deficit.
Can I lose weight without counting calories?
Yes — every effective approach works by creating a deficit, whether you count or not. Higher-protein meals, more whole foods, fewer liquid calories and consistent meal timing all reduce intake without arithmetic. Counting is simply the most direct way to know whether a deficit exists when progress stalls.