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Muscle gain calculator
Enter your sex, bodyweight and how many years you have trained consistently. The calculator gives a realistic range for the muscle you can add in a month and over the next year, and shows how that rate slows with each year of training.
Example result
~0.75–1.13kg
~9.0–13.5kg
| Training | Per month | Per year |
|---|---|---|
| Under 1 year | 0.75–1.13 kg | 9.0–13.5 kg |
| 1–2 years | 0.38–0.75 kg | 4.5–9.0 kg |
| 2–4 years | 0.19–0.38 kg | 2.3–4.5 kg |
| 4+ years | 0.08–0.11 kg | 0.91–1.36 kg |
Muscle gain examples
The rate depends on who is lifting and for how long. What to do with it changes too.
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Example 1
A first-year lifter at 150 lb
A man in his first year of consistent training who weighs 150 lb.
- Sex
- Male
- Years of consistent training
- Under 1 year
- Bodyweight
- 150 lb
- Muscle you can add in a month~1.5–2.3 lb
- Over the next year~18.0–27.0 lb
This matches the 150 lb beginner in McDonald's worked example. If his scale weight climbs much faster than this range, most of the extra isn't muscle, so trim the calorie surplus rather than the training.
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Example 2
A woman starting out
A woman at 60 kg in her first year of lifting.
- Sex
- Female
- Years of consistent training
- Under 1 year
- Bodyweight
- 60 kg
- Muscle you can add in a month~0.30–0.45 kg
- Over the next year~3.6–5.4 kg
Under half a kilo a month won't show on a bathroom scale. Judge the first months by her training log and a tape measure, which this guide walks through.
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Example 3
Year three, 85 kg
A man in his third year of training at 85 kg, frustrated that the scale has stalled.
- Sex
- Male
- Years of consistent training
- 2–4 years
- Bodyweight
- 85 kg
- Muscle you can add in a month~0.21–0.42 kg
- Over the next year~2.5–5.1 kg
A month is the wrong unit at this stage. Plan in blocks instead: a 12-week block adds up to about a kilogram, and the block is judged by whether his working weights went up.
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Example 4
Ten years in
A lifter who has trained seriously for a decade and weighs 190 lb.
- Sex
- Male
- Years of consistent training
- 4+ years
- Bodyweight
- 190 lb
- Muscle you can add in a month~0.17–0.25 lb
- Over the next year~2.0–3.0 lb
A bulk aimed at a pound a week would outrun this rate more than tenfold, so most of that weight would be fat. A small surplus, or none, fits better, and the progress to chase is in the log.
How much muscle can you gain in a month?
Less every year. In the models this calculator uses, a man in his first year can add about 1 to 1.5% of his bodyweight a month, half that in his second year, and half again in the third and fourth. After four years McDonald puts it at 2 to 3 lb a year. Women gain about half as much.
Research agrees on the scale. A meta-analysis of 111 studies in men found resistance training added about 1.5 kg of muscle (95% CI 1.30 to 1.76) over programs that averaged about 10 weeks. That works out to roughly 0.6 kg a month, a little under the first-year range for a 70 kg man, so treat the top of each range as a ceiling.
What counts as a year of training
McDonald counts years of proper training, not years of gym membership. Someone who trained poorly for four years may still have close to first-year potential once they start training properly, so pick the tier that matches how long you have trained hard and consistently.
Across a whole career, McDonald puts the total at roughly 40 to 50 lb of muscle for men, most of it in the first four years or so. Check how much you carry now with the FFMI calculator.
How the estimate is built
No controlled study reports monthly muscle gain by years of training, so the calculator uses two coaching models as Lyle McDonald sets them out. The first four years follow the Aragon/Helms model: 1 to 1.5% of bodyweight a month in the first year, 0.5 to 1% in the second, and 0.25 to 0.5% in the third and fourth. After four years it uses McDonald's own table, 2 to 3 lb a year for men. Women get half of each figure, as both models do.
Aragon/Helms is a rate of weight gain. Like McDonald's worked example, this page reads it as muscle. Benito et al. (2020) is the research check described above.
monthly gain = bodyweight × rate for your training years (× 0.5 for women)
75 × 1% = 0.75 kg, 75 × 1.5% = 1.125 kg, shown as 0.75–1.13 kg a month
× 12 = 9.0–13.5 kg over a yearMake it fit you
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Pick the tier by consistent years
Count the years you trained hard and regularly. Two years of on-and-off sessions is closer to one.
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Plan in blocks, not months
Multiply the monthly range by the length of your next block. Past the first year, a month's gain is too small to measure on its own.
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Weigh in often, judge the average
Weigh yourself several mornings a week and compare monthly averages. If the average climbs well past the top of your range, ease off the surplus.
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Older lifters
McDonald notes that older lifters gain more slowly than younger ones. Start from the lower end of your range.
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Let the log confirm it
Rising working weights at the same reps and reps in reserve are the everyday sign that training is working. If they stall for a whole block, change the training before the diet; the progressive overload calculator plans the next jumps.
Questions
How much muscle can you gain in a month?
About 1 to 1.5% of bodyweight for a man in his first year, half that in year two and less after. For a 75 kg beginner that's 0.75 to 1.13 kg a month at best; women gain about half as much.
How much muscle can a beginner gain in a year?
McDonald's worked example puts a 150 lb man at 18 to 27 lb in his first year, the top of what the models allow. Research averages are lower, about 1.5 kg over 10-week programs.
Can women build muscle as fast as men?
Both models this calculator uses give women about half the men's rate, so at the same bodyweight the women's ranges are half the men's.
Can you gain 1 kg of muscle in a month?
Only at the top of the first-year range for a man heavier than about 67 kg. For everyone else, and after the first year, a kilogram takes several months.
What is my maximum muscular potential?
McDonald estimates roughly 40 to 50 lb of muscle over a man's lifting career, reached over 4 or more years of proper training, and perhaps 17 to 21 lb for women.
How many calories do I need to build muscle?
This calculator sets the rate to aim for, not the calories. Pick a surplus, then check it against your range: if your average bodyweight climbs far faster, the surplus is bigger than the muscle can use.
Related calculators and templates
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FFMI calculator
How much lean mass you carry now, for your height.
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How many sets per muscle group per week?
Weekly sets that drive the gain.
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Bench press progression calculator
When to add weight as you grow.
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Am I gaining muscle or fat?
What the scale won't tell you.
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Newbie gains
How long the fast first phase lasts.
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Best workout plan for muscle gain
A plan built for this rate.
Sources
See the gain in your lifts, not just the scale
RIRLift logs load, reps and reps in reserve on every set, tracks your bodyweight beside each lift's trend, and sets your next weights from what you logged.
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