Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate your FFMI, a height-normalized measure of muscularity used in strength sports.
FFMI is a height-normalized version of lean body mass (Kouri et al., 1995), widely used in strength-sports literature to compare muscularity across people of different heights -- similar in spirit to how BMI normalizes weight by height.
Enter your weight, height, and sex. Lean mass is first estimated (Boer formula), then normalized into FFMI and a height-adjusted FFMI.
FFMI = Lean Body Mass(kg) / Height(m)²
Normalized FFMI = FFMI + 6.1 × (1.8 - Height(m))
The normalization adjusts for the fact that taller individuals naturally carry more lean mass, making FFMI comparable across different heights.
Commonly referenced in strength-sports/bodybuilding contexts to gauge how muscular someone is independent of height -- a "natural" FFMI ceiling is often cited around 25, though this varies by individual genetics.
The tool's default inputs are 80 kg, 180 cm, and male. Lean mass is first estimated with the Boer formula for men: 0.407 x 80 + 0.267 x 180 - 19.2, which is about 61.4 kg. Height is 1.80 m, so FFMI is 61.4 divided by 3.24, about 18.96. The normalization term is 6.1 x (1.8 - 1.8), which is zero, so the normalized value is also about 18.96. For someone 1.90 m tall, the normalization adds 6.1 x (1.8 - 1.9), which subtracts 0.61, and for someone 1.70 m tall it adds 0.61.
Lean mass = 0.407 x 80 + 0.267 x 180 - 19.2 = 61.4 kg. FFMI = 61.4 / 1.8^2 = 18.96.
This calculator does not ask for body fat percentage. It estimates lean mass purely from weight, height, and sex using the Boer equation, a population-level formula. That means two people with the same weight, height, and sex always get identical results, even if one lifts seriously and the other does not. The output is therefore a rough population-based estimate, not a measurement of your actual muscle. If you know your lean mass from a DEXA scan, bioimpedance device, or skinfold assessment, dividing that lean mass in kilograms by height in meters squared will give a truer FFMI than this estimate.
Because the lean-mass input here is formula-driven, the FFMI it reports mostly tracks body weight and height. Gaining weight raises the estimate whether the gain is muscle or fat, which is the opposite of what a truly measured FFMI would do. Use this tool for a ballpark comparison or a starting point, and be cautious about reading it as proof of training progress. Reference ranges for FFMI are rough and vary across sources and individuals.
This tool is educational and not medical advice. For body composition decisions, or concerns about supplements or performance claims, consult a qualified professional.
Commonly cited ranges put an average untrained FFMI around 18-20 and well-trained natural lifters around 21-23, though individual genetics vary widely -- treat any specific number as a rough reference, not a target.
Taller people naturally have more lean mass at the same body-fat level, so a raw FFMI comparison would unfairly favor shorter people -- the height adjustment corrects for this.
FFMI is lean body mass normalized by height squared -- see the Lean Body Mass Calculator for the underlying lean-mass estimate.
No. Lean mass is estimated from weight, height, and sex using the Boer formula, so the result is an estimate and does not reflect your actual body fat.
Because the lean-mass estimate is formula-based on total weight, any weight gain increases it. A measured lean-mass value would separate muscle from fat.
Weight is entered in kilograms and height in centimeters. Convert pounds and inches first if needed.
The height adjustment is zero at 1.8 m (180 cm), so at or near that height FFMI and normalized FFMI are the same or nearly so.
Reference: Centers for Disease Control and Prevention