Online Tool Store
Calorie Deficit Calculator
Calculate your daily calorie target for a steady, sustainable weight loss goal from your age, sex, height, weight, and activity level. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example shown — replace it with your own numbers.
How it works
- Enter your sex, age, height, weight, and how active you typically are.
- Pick a steady weekly weight-loss goal — from a gentle 0.25 kg/week up to the generally recommended maximum of 1 kg/week.
- Your maintenance calories, the daily deficit needed, and your target daily calories update as you type.
The formula
Resting calorie needs (BMR) come from the Mifflin-St Jeor equation:
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Multiplying BMR by an activity factor (1.2 for sedentary up to 1.9 for very active) gives your maintenance calories — the amount that keeps your weight steady. Since roughly 7,700 kcal correspond to 1 kg of body fat, your weekly weight-loss goal converts to a daily deficit:
daily deficit = (weekly loss (kg) × 7,700) / 7
Target daily calories = maintenance calories − daily deficit. Example: a 32-year-old man, 170 cm and 82 kg, lightly active, has a maintenance intake of roughly 2,375 kcal — aiming for 0.5 kg/week trims about 550 kcal a day, for a target of roughly 1,825 kcal.
This is an estimate based on population-average formulas, not a medical calculation — individual metabolism varies. Talk to a healthcare professional before starting an aggressive deficit or if you have a health condition.
FAQ
How is this different from a maintenance calorie calculator?
It starts with the same maintenance-calorie estimate (your TDEE), then subtracts the daily calorie deficit needed to lose weight at the steady weekly rate you choose — so you get a target to eat toward, not just your baseline.
Why does it warn me my target is too low?
Going below roughly 1,200 kcal/day for women or 1,500 kcal/day for men is generally not recommended without medical supervision — it can be hard to get enough nutrients and hard to sustain. If you see the warning, pick a smaller weekly goal or a higher activity level instead of pushing the deficit further.
What formula does it use for calorie needs?
The Mifflin-St Jeor equation for resting metabolic rate (BMR), scaled by an activity multiplier to estimate your Total Daily Energy Expenditure (TDEE) — the most widely validated formula for this and the one most calorie calculators use.
Why 7,700 kcal per kilogram of fat, not a rounder number?
1 kg of body fat stores roughly 7,700 kcal of energy (about 3,500 kcal per pound) — that figure, not a rounder one, is the commonly cited conversion used to translate a weekly weight-loss goal into a daily calorie deficit.
Is my information sent anywhere?
No. Every calculation happens locally in your browser using plain JavaScript — none of your age, weight, height, or goals are uploaded or logged anywhere.
How we compare
| Feature | Online Tool Store | Typical fitness app calculators | Generic BMR-only calculators |
|---|---|---|---|
| No sign-up or app install | ✓ | ✗ | ✓ |
| Converts your goal directly into a daily calorie target | ✓ | ✓ | ✗ (BMR only) |
| Warns if your target drops below a safe minimum | ✓ | Varies by app | ✗ |
| Free, no premium tier, no ads | ✓ | Varies — many gate goal-tracking behind sign-up | ✓ |
If you just want a straightforward, private daily calorie target for a steady weight-loss goal — not another account to sign up for — Calorie Deficit Calculator gets you there in one page, with a built-in check against going too low.