Calorie Deficit Calculator
How many calories should you cut per day to hit a weight-loss goal — or how long will a given daily deficit take? One equation, both directions, with safety bands.
Your deficit
TDEE context (for the safe-intake check)
Result
Weekly projection
| Week | Total lost (kg) | That week's deficit (kcal) |
|---|
Methodology
All results come from one rule of thumb used in weight-loss planning:
- Target → deficit: daily deficit = kg × 7,700 ÷ (weeks × 7)
- Deficit → timeline: weeks = kg × 7,700 ÷ (daily deficit × 7)
- Loss rate: kg per week = daily deficit × 7 ÷ 7,700 (≈ deficit ÷ 1,100)
1 kg of body fat stores roughly 7,700 kcal. A 500 kcal/day deficit therefore loses about 0.45 kg/week; 550 kcal/day loses about 0.5 kg/week; 1,100 kcal/day loses about 1 kg/week.
Safety bands (general guidelines, not personal advice): a safe calorie deficit for most healthy adults is 500–750 kcal per day — enough to lose about 0.5–0.75 kg per week while keeping intake above safe floors. Above 750 is aggressive; above 1,000 is flagged dangerous; intake floors of about 1,200 kcal/day (women) and 1,500 kcal/day (men) are checked against your estimated TDEE (Mifflin-St Jeor). Real bodies are not linear — plateaus, water weight, and metabolic adaptation mean the projection is an idealized trend, not a promise.
Frequently asked questions
What is a calorie deficit?
A calorie deficit means you consume fewer calories than your body burns (your TDEE) each day. The shortfall forces your body to use stored fat for energy. Roughly 7,700 kcal of cumulative deficit equals about 1 kg of body fat lost.
How do I calculate my daily calorie deficit?
Multiply the kilograms you want to lose by 7,700, then divide by the number of days in your timeframe. Example: losing 5 kg in 10 weeks (70 days) needs a daily deficit of 5 x 7,700 / 70 = 550 kcal per day. This calculator works in both directions: target to deficit, or deficit to timeline.
Is a 500 calorie deficit per day safe?
Yes. A 500 kcal/day deficit is the classic guideline, producing about 0.5 kg of loss per week (500 x 7 / 7,700 is about 0.45 kg). Most guidelines treat 500-750 kcal/day as a safe, sustainable band for most healthy adults.
Is a 1,000 calorie deficit too much?
For most people, yes. Deficits above 1,000 kcal/day are flagged as dangerous by this tool: they commonly cause muscle loss, fatigue, nutrient gaps, and rebound weight gain. Talk to a clinician before attempting an aggressive deficit.
How long will it take to lose 5 kg? 10 kg?
At a 550 kcal/day deficit (about 0.5 kg per week), 5 kg takes roughly 10 weeks and 10 kg takes roughly 20 weeks. Use the deficit-to-timeline mode above with your own daily deficit to get your exact projection.
What is the minimum safe calorie intake?
Common floors are about 1,200 kcal/day for women and 1,500 kcal/day for men. This calculator warns you when your planned deficit would push intake below these floors. These are general guides, not personal medical advice.
Why am I not losing weight in a calorie deficit?
Common reasons: the deficit is smaller than estimated (tracking errors, uncounted snacks or drinks), water retention masking fat loss, metabolic adaptation over long diets, or the 7,700 kcal/kg rule being an average that varies between people. Track for 3-4 weeks and adjust based on the trend, not day-to-day noise.
How is this different from the BMI weight-loss planner or the calorie calculator?
Scope boundary: this tool is a pure deficit solver. It converts between kilograms, daily deficit, and weeks. The BMI Weight Loss Planner plans a BMI-based goal with a weekly projection and TDEE context, and the Calorie Calculator estimates your general daily calorie needs (TDEE/macros) without solving a deficit timeline.
Free tool by NRTechStudio