Maximum Muscular Potential Calculator

It estimates the drug-free ceiling for your lean body mass and total bodyweight at a body fat level you choose. The calculation uses the Casey Butt model, which predicts how much muscle a natural lifter can build from frame size (wrist and ankle circumference) and height. Think of it as a long-term target for a fully developed, lean physique, not a starting point.

Lean body mass in pounds equals your height in inches raised to the power 1.5, multiplied by the sum of the square root of your wrist circumference divided by 22.6670 and the square root of your ankle circumference divided by 17.0104, then multiplied by your body fat percent divided by 224 plus 1. Your total muscular bodyweight is that lean mass divided by (1 minus your body fat as a decimal). Height, wrist, and ankle are measured in inches, and the result is in pounds, which this tool also converts to kilograms.

Wrist and ankle circumference are proxies for the size of your skeletal frame, which sets a practical limit on how much muscle your joints and bones can support. Unlike weight or muscle size, these measurements barely change with training, so they anchor your genetic potential. Casey Butt found that bigger-framed lifters tend to carry more drug-free muscle at the same height.

No, it is a statistical estimate drawn from elite drug-free male bodybuilders, so it describes a typical ceiling rather than a hard wall. Some people exceed it and many never reach it, since training history, recovery, age, and consistency all play a role. Use the number as a motivating benchmark and a reality check on bulking goals, not a verdict.

The model was built from male bodybuilder data, so it is most accurate for men. Women naturally carry less fat-free mass for the same frame, so a woman's realistic ceiling sits well below the figure shown here. If you are a woman, treat the output as a rough, male-referenced upper bound rather than a personal target.

No. This calculator is for education and motivation only and is not a substitute for professional medical, nutrition, or coaching advice. Talk to a qualified professional before making major changes to your training or diet, especially if you have a health condition.