Calorie Deficit Calculator
Find the daily calories to hit a target weekly weight-loss rate.
Results update as you type.
About this calculator
A calorie deficit calculator works out how many calories to eat below your maintenance level to lose weight at a chosen pace. It uses the widely-used approximation that a kilogram of body fat stores about 7,700 calories (3,500 per pound), so a 500-calorie daily deficit loses roughly half a kilogram (about a pound) a week. Add your current and goal weight to estimate how long it will take.
The daily deficit is the weekly weight-loss goal turned into calories per day: deficit = rate × calories-per-kg ÷ 7. Suppose your maintenance (TDEE) is 2,200 kcal and you want to lose 0.5 kg a week. That is 0.5 × 7,700 ÷ 7 = 550 calories a day, so your target intake is 2,200 − 550 = 1,650 kcal. Switch to imperial and the tool uses 3,500 calories per pound instead.
Get your maintenance number first from a TDEE calculator, then use this tool to choose a sustainable pace — commonly 0.25–1 kg (0.5–2 lb) per week. Fill in your current and goal weight and it also estimates the number of weeks to reach the goal at that rate. This is general guidance for healthy adults, not medical or dietary advice.
Frequently asked questions
How big a calorie deficit is safe?
A deficit of 500–750 calories a day (0.5–0.75 kg or about 1–1.5 lb per week) is a common, sustainable target. Very aggressive deficits risk muscle loss and are hard to maintain, so most guidance keeps loss to about 1% of body weight per week.
Why 7,700 calories per kilogram?
A kilogram of stored body fat holds roughly 7,700 calories (a pound about 3,500). Dividing your weekly deficit by seven gives the daily deficit this calculator subtracts from your maintenance calories.
Is weight loss exactly this linear?
No. The 3,500-calorie rule is an approximation. As you lose weight your maintenance calories fall, water shifts and metabolism adapts, so real loss usually slows over time. Treat the estimate as a starting point and adjust.
How long will it take to lose 10 kg?
With your current and goal weight entered, weeks = (current − goal) ÷ weekly rate. Losing 10 kg at 0.5 kg per week takes about 20 weeks, or roughly 4.6 months. The tool shows this time-to-goal whenever both weights are filled in.
What should I eat while in a deficit?
This tool gives the calorie number; a macro or protein calculator turns it into food. Keeping protein high — around 1.8–2.2 g/kg — during a deficit helps preserve muscle so most of the weight you lose is fat.
Can I lose weight without a calorie deficit?
No. Weight loss requires burning more energy than you take in, so the deficit is the whole mechanism. You can create it by eating less, moving more, or both.
Can my calorie target go too low?
Yes. Subtracting a large deficit from a low maintenance can leave very few calories. Most guidance keeps intake above roughly 1,200 kcal for women and 1,500 for men; if your target drops below that, pick a slower rate of loss.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/calorie-deficit/curl
curl "https://calculator.free/api/v1/calorie-deficit/?maintenance=2200&units=metric&rate=0.5"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/calorie-deficit/?" + new URLSearchParams({
"maintenance": "2200",
"units": "metric",
"rate": "0.5"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.