Maximum Muscular Potential Calculator

About this calculator

Formulas for natural maximum muscular potential — popularized by researcher Casey Butt's regression model and echoed in Martin Berkhan's simplified version — estimate the largest lean body weight a natural (non-steroid-using) athlete can realistically build at a given body fat percentage, using height along with wrist and ankle circumference as proxies for skeletal frame size. The underlying premise is that muscle mass is bounded by joint and bone structure — someone with a larger frame (thicker wrists and ankles relative to height) has more room to add muscle than someone with a smaller frame, regardless of training.

Bodybuilders, strength coaches, and drug-testing federations reference these genetic-potential formulas both as realistic long-term goal-setting tools for natural lifters and, more controversially, as a rough screening heuristic for identifying physiques that may exceed what's achievable naturally, since Butt's model was built from data on drug-tested elite natural bodybuilders.

This calculator takes your height, wrist and ankle circumference, and target body fat percentage to estimate your natural maximum muscular body weight potential.