Comprehensive Calculator Guide
A calorie deficit means eating less than you burn, so the body draws on its fat stores. This calculator estimates how long a daily deficit takes to reach your goal weight, using about 7,700 kcal per kilogram of body fat. Going from 90 to 80 kg at 500 kcal a day takes about 154 days.
The 7,700 rule and a sensible deficit
Body fat holds roughly 7,700 kcal per kilogram, so 500 kcal a day is about half a kilo a week. It is a simplification: loss slows as you get lighter and the body adapts, so treat the result as a rough minimum.
Many guidelines suggest 500–750 kcal a day. Larger deficits risk muscle loss and fatigue and are hard to keep up. People with chronic illness, or who are pregnant or breastfeeding, should ask a doctor first.
How to Use
- 01Enter current and goal weight.
- 02Enter the daily deficit.
- 03Read days, weeks and weekly loss; or enter days to get the deficit.
Formula Used
Days = (current − goal) × 7700 ÷ daily deficitPractical Examples
Example 1
90 to 80 kg at 500 kcal: 154 days.
Example 2
85 to 78 kg at 750 kcal: about 72 days.
Example 3: reverse
5 kg in 60 days needs about 642 kcal a day.
Important Tips
- Keep protein up and lift weights to protect muscle.
Common Mistakes to Avoid
- Expecting the same pace all the way to the goal.
Frequently Asked Questions
- How many calories make a kilo?
- About 7,700.
- How much will 500 kcal a day lose?
- About half a kilo a week at first.
- Why does loss slow down?
- A lighter body burns less and adapts to the deficit.