Clinical Accuracy Verified
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Natural Muscular Potential
Predict your maximum drug-free muscle size (FFMI) based on your wrist and ankle bone structure.
in
Example: 5'10" is 70 inches.
in
Measure the smallest part of your wrist, below the bone.
in
Measure the smallest part of your ankle, above the bone.
%
🧬 Genetic Limit Prediction
Max Lean Body Mass180 lbs
Total Weight @ 10% BF200 lbs
FFMI Score25.8
Maximum Measurements
Chest
48.3"
Biceps
18"
Thighs
42.4"
Calves
29.1"
⚠️ An FFMI over 25 is generally considered the upper limit for natural bodybuilders. You have elite genetics!
Casey Butt's Model
Developed by analyzing elite drug-free bodybuilders (pre-steroid era). It uses bone structure to determine the maximum amount of muscle a frame can support.FFMI (Fat Free Mass Index)
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