The MuscleFlare flagship
How much muscle can you realistically build?
Enter your height, weight and body-fat estimate. MuscleFlare compares your fat-free mass to where drug-free lifters of your sex and height typically top out, then projects how the gap closes with good training. You get ranges, not false precision.
Your numbers
From a DEXA scan, calipers, a smart scale or the tape method.
Frame & measurements Pro
Wrist and ankle size reflect skeletal frame and refine your ceiling (men). Current measurements are compared with per-muscle targets.
Smallest point
Smallest point
Your potential appears here
Enter sex, age, height, weight and a body-fat estimate. Not sure of your body fat? Use the tape measure or pick the description that fits.
How the estimate works
1 · Where you are
Lean mass = weight × (1 − body fat). Your height-normalised FFMI (Kouri et al., 1995) puts that lean mass on a scale that is fair across heights.
2 · Where people like you top out
The typical drug-free ceiling is a normalised FFMI of ~24 for men (range 22.5–25.5) and ~20 for women (18.5–21.5). Converted back to your height, that is your ceiling lean mass — shown as a range, because genetics vary.
3 · How fast the gap closes
Each year of good training closes a share of the remaining gap: about 60% in the first year for a young male beginner, less with more training years, for women and with age. That reproduces the familiar “~10 kg, then 5, then 2–3” pattern.
4 · Pro: your frame
With wrist and ankle measurements, the Advanced Report applies Casey Butt’s frame model — built from drug-free champions — for a skeletal-frame-adjusted ceiling and per-muscle targets.
Questions
How accurate is a muscle potential calculator?
It is a population estimate. It tells you where people with your height and sex typically top out and how quickly they get there — not what you personally will reach. Genetics and the accuracy of your body-fat estimate move the answer by several kilograms either way, which is why every result is shown as a range.
What is the natural limit for FFMI?
In the most cited study (Kouri et al., 1995), drug-free male lifters rarely exceeded a height-normalised FFMI of about 25. Most trained men plateau between roughly 22 and 24. For women, the equivalent range is about 18.5–21.5, though the research is much thinner.
How fast can I build muscle naturally?
Men who train and eat well typically gain around 9–11 kg of lean mass in the first year, roughly half that in the second, and less every year after. Women typically gain about half as much in absolute terms. The chart shows this curve for your numbers.
Does age limit how much muscle I can build?
Age slows the rate more than it lowers the ceiling. The model reduces expected yearly gains from about 40 onwards — muscle can still be built at any age with progressive training and enough protein.
Why do you need my body fat?
Muscle potential is about lean mass, and lean mass is bodyweight minus fat. Without a body-fat estimate there is no way to separate the two. If you do not know it, use the tape-measure option or pick the description that fits best.