FFMI

The formula is simple: FFMI = lean mass (kg) / height (m) squared. To calculate lean mass, subtract fat mass from total weight. Example: you weigh 85 kg with 15% body fat. Your lean mass is 72.25 kg. If you're 1.80 m tall, your FFMI is 72.25 / (1.80 x 1.80) = 22.3.

Reference values for men: under 18 indicates low muscle mass, 18-20 is average, 20-22 is above average (someone who has been training seriously for a few years), 22-25 is an advanced level reachable naturally with years of training and favorable genetics. Values above 25 are extremely rare without anabolic steroid use. For women, values are about 3-4 points lower.

Why is it useful? First: it gives you an objective parameter to evaluate your muscular development over time, independent of body fat percentage. Second: it helps you understand how close you are to your natural genetic potential. An FFMI of 25 for a natural is an elite achievement that requires years of optimal training, nutrition and recovery.

Watch out for the limits: FFMI depends on the precision of the body fat measurement, which can vary widely depending on the method used (bioimpedance, skinfold calipers, DEXA). Don't take the number as an absolute verdict. Use it as a long-term reference, comparing measurements always taken with the same method and under the same conditions.