Weight Gain from a Surplus
A kilogram of body weight is treated as roughly 7,700 kcal. Multiply the daily surplus by seven for a week and divide. A 300 kcal surplus gives about 0.27 kg a week.
Your numbers
Gain a week
0.273kg
Difference
3.27kg
Calories
25,200kcal
What it means
0.273 kg a week is the lean-gain pace; with resistance training most of it is muscle.
Formula
Gain a week = Daily surplus × 7 ÷ 7700
The 7,700 figure is for fat, so muscle gain deviates. Real-world gain ranges from half to double this depending on metabolic adaptation.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Daily surplus (kcal)The daily calories you eat beyond what you burn — the fuel for gaining. | 300 | 0 ~ 2,000 |
| Time needed (wk)Weeks to the goal if you keep this pace. | 12 | 1 ~ 104 |
Step by step
Quick reference table
Results when only Daily surplus (kcal) changes and everything else stays put.
| Daily surplus (kcal) | Gain a week (kg) | Difference (kg) | Calories (kcal) |
|---|---|---|---|
| 150 | 0.136 | 1.64 | 12,600 |
| 225 | 0.205 | 2.45 | 18,900 |
| 300 | 0.273 | 3.27 | 25,200 |
| 450 | 0.409 | 4.91 | 37,800 |
| 600 | 0.545 | 6.55 | 50,400 |
What each result means
| Result | At default values |
|---|---|
| Gain a week (kg)The weight gained in a week if that surplus holds. | 0.273 |
| Difference (kg)The gap between two values — a quantity, not a rate. | 3.27 |
| Calories (kcal)Energy, in kilocalories. | 25,200 |
Common mistakes
The 7,700 figure is for fat, so muscle gain deviates. Real-world gain ranges from half to double this depending on metabolic adaptation.
Glossary
- Daily surplus
- The daily calories you eat beyond what you burn — the fuel for gaining.
- Time needed
- Weeks to the goal if you keep this pace.
- Gain a week
- The weight gained in a week if that surplus holds.
- Difference
- The gap between two values — a quantity, not a rate.
- Calories
- Energy, in kilocalories.
Frequently asked questions
Q. How is Weight Gain from a Surplus calculated?
Gain a week = Daily surplus × 7 ÷ 7700 — A kilogram of body weight is treated as roughly 7,700 kcal. Multiply the daily surplus by seven for a week and divide. A 300 kcal surplus gives about 0.27 kg a week.
Q. Can you walk through an example?
With Daily surplus 300kcal, Time needed 12wk, the answer is Gain a week 0.273kg.
Q. What do I need to enter?
Enter Daily surplus, Time needed. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Daily surplus (kcal) moves the answer to Daily surplus (kcal) 150 → Gain a week (kg) 0.136 and Daily surplus (kcal) 600 → Gain a week (kg) 0.545. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
The 7,700 figure is for fat, so muscle gain deviates. Real-world gain ranges from half to double this depending on metabolic adaptation.
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These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.