Know your numbers
Bulking calculator
The fastest way to build muscle is not the biggest surplus — it is the smallest surplus that supports growth. Beginners can gain faster; experienced lifters who eat too much just gain fat. This calculator sets the rate by experience.
Your numbers
Training 3–5 days a week with a normal daily step count
Your bulking calories appear here
Enter age, height, weight and activity. Experience sets how fast you can realistically gain.
How it’s calculated
Rate of gain
Following Alan Aragon’s widely used guideline, target a monthly gain of 1–1.5% of bodyweight as a beginner, 0.5–1% as an intermediate and 0.25–0.5% as an advanced lifter.
Surplus
We convert the rate to calories using ~5,500 kcal per kg gained — a middle estimate for a mix of lean and fat tissue. It is an approximation; after three weeks your scale trend tells you the real number.
Adjusting
Weigh daily and compare weekly averages. Gaining faster than target: remove 100–150 kcal. Flat for two weeks: add 100–150 kcal.
Full sources and limitations are on the methodology page. Estimates are for healthy adults and are not medical advice.
Questions
Should I “dirty bulk”?
No. Beyond a modest surplus, extra calories become fat, not muscle — and then have to be dieted off.
Should I cut before I bulk?
If you are above ~20% body fat (men) or ~30% (women), usually yes: a leaner start leaves more room to gain before you need to diet again.