MathIsimple

FFMI Calculator

Calculate Fat-Free Mass Index (FFMI) to compare muscle mass across different body sizes. Enter weight, height, and body fat to view FFMI, normalized FFMI, lean mass, BMI, and classification guidance.

Free online calculator BMI + FFMI metrics Body composition insights

Body composition inputs

Select measurement system, body fat percentage, and sex to tailor results.

Fitness & Health

Use scale weight. Convert from pounds if using metric inputs.

Height directly influences normalized FFMI.

Use DEXA, caliper, or bioimpedance measurements for accuracy.

Used for interpretation guidance—FFMI formula applies to all.

How to use this FFMI calculator

Select measurement units, enter weight, height, and body fat, then press “Calculate FFMI.” The tool returns FFMI, normalized FFMI, lean mass, and BMI.