Maximum Muscular Potential Calculator
How much muscle can you build naturally? Enter your frame measurements to see your genetic ceiling based on four peer-reviewed models — personalised to your skeleton, not just your height.
Max lean mass
74.1–80.4 kg
How to measure
- Wrist: Wrist: Around the narrowest point, just above the wrist bone (below the bump). Use a flexible tape measure.
- Ankle: Ankle: Around the narrowest point, just above the ankle bone. Keep tape flat and snug but not tight.
Your maximum lean muscle mass
74.1–80.4 kg
consensus across 3 models
Your progress toward genetic potential
90%
You are an advanced natural lifter, well into diminishing returns territory. Every extra kg of muscle is hard-won.
Max lean mass by model
Max total weight
91.4 kg
at 12% body fat (Casey Butt)
Remaining potential
9.2 kg
after 1 year training (McDonald)
Contest weight (5% BF)
78 kg
Berkhan formula
Weight at 12% BF
84.2 kg
Berkhan adjusted
Expected muscle gain by year (McDonald model)
Maximum body part circumferences
At your genetic potential (Casey Butt model)
| Body part | Max circumference |
|---|---|
| Chest | 114.4 cm |
| Bicep (flexed) | 42.1 cm |
| Thigh | 65.5 cm |
| Calf | 43.2 cm |
| Forearm | 33.5 cm |
| Neck | 40.9 cm |
How it works
This calculator combines four independent models to estimate your natural muscular ceiling. Casey Butt uses your skeletal frame (wrist and ankle size) — the most personalised approach. Martin Berkhan uses a simple height-based formula validated against drug-tested competitors. FFMI-based uses the Kouri et al. (1995) finding that an FFMI above 25 is extremely rare in natural athletes. Lyle McDonald predicts how quickly you can get there — gains are fastest in year 1 and diminish each year.
Important: These are statistical estimates based on population averages. Individual genetics vary significantly — some people may exceed these estimates, others may fall short. Wrist/ankle measurements are proxies for skeletal frame size, not perfect predictors. These models were primarily developed studying male bodybuilders; female estimates are adapted and have wider uncertainty.
Sources: Casey Butt (2010) "Your Muscular Potential" 4th ed.; Martin Berkhan, Leangains.com — "Maximum Muscular Potential of Drug-Free Athletes"; Lyle McDonald, BodyRecomposition.com — "What's My Genetic Muscular Potential?"; Kouri et al. (1995) "Fat-free mass index in users and nonusers of anabolic-androgenic steroids", Clinical Journal of Sport Medicine 5(4):223–228; Janssen et al. (2000) J Appl Physiol — skeletal muscle mass sex differences.