THE NUMORIX GUIDE
How to use the Lean Mass Index Calculator
Last reviewed September 14, 2026
What this calculator does
The engine converts height from centimeters to meters and divides lean body mass in kilograms by height in meters squared: LMI = leanBodyMass / heightMeters^2.
Formula and method
The engine converts height from centimeters to meters and divides lean body mass in kilograms by height in meters squared: LMI = leanBodyMass / heightMeters^2. It labels values below 15 Very Low, 15-<17 Low, 17-<19 Normal, 19-<21 Above Average, and 21 or higher High.
Variables and inputs
Enter lean body mass in kilograms and height in centimeters. The result is an index in kg/m2, displayed to two decimals. The route does not ask for sex, age, how lean mass was measured, or whether the value is total or appendicular lean mass.
Worked example
For 55 kg of lean body mass and 170 cm height: height = 1.70 m; LMI = 55 / (1.70 * 1.70) = 19.03 kg/m2. Because 19.03 is at least 19 and below 21, the engine returns Above Average.
How to interpret the result
LMI normalizes an entered lean-mass estimate for height. The category is the route's simple threshold system, not a universal reference standard; the reliability of the index depends on the method used to estimate lean mass.
Common mistakes to avoid
Enter lean mass rather than total body weight, convert height to centimeters as labeled, and do not combine a DXA-derived lean mass with a formula-based category without noting the method. Keep kg and cm consistent.
Assumptions and limitations
The cutoffs are hardcoded and do not vary by sex, age, ethnicity, training status, or measurement technology. The engine does not validate positive inputs or distinguish whole-body LMI from appendicular lean-mass index. A low or high label is not a diagnosis of malnutrition or athletic status.