Comprehensive Calculator Guide
This calculator tells you how many days and weeks it takes to reach a goal weight if you eat a steady surplus above your needs each day. Going from 60 to 66 kg on a 350-calorie surplus takes about 132 days, close to 19 weeks at 0.32 kg a week. It also tells you whether that pace suits building muscle or leans toward adding fat.
The 7,700-calorie rule and a sensible pace
A kilo of body fat stores roughly 7,700 calories, so a 350-calorie daily surplus adds about a kilo every 22 days. It’s an approximation: muscle gain needs fewer calories per kilo, and your body burns a little more when you eat more.
For lean gains, a 250–500 calorie surplus — about 0.25–0.5 kg a week — with resistance training and enough protein works best. If you’re underweight for no clear reason, see a doctor first.
How to Use
- Enter your current and goal weight.
- Enter the daily calorie surplus you plan to eat.
- Press “Work out the time” to see the days, weeks and weekly gain.
Formula Used
Days = (goal − current weight) × 7,700 ÷ daily surplus
Practical Examples
- Example 1
- 60 to 66 kg at +350 calories: 132 days, 18.9 weeks, 0.32 kg a week.
- Example 2
- 55 to 58 kg at +500 calories: 46.2 days, 6.6 weeks, 0.45 kg a week.
Important Tips
- Work out your maintenance calories first, then add the surplus.
Common Mistakes to Avoid
- Relying on sweets and soft drinks for the extra calories.
Frequently Asked Questions
- How many calories to gain a kilo?
- About 7,700 above your needs.
- How fast can I gain healthily?
- Roughly 1–2 kg a month on a 250–500 calorie surplus.
- How do I gain weight without fat?
- A moderate surplus, about 1.6 g of protein per kg and regular resistance training.