Muscle Mass Index Calculator

About this calculator

The muscle mass index divides your total muscle mass by the square of your height (kg/m²), mirroring the structure of BMI (which uses total body weight instead) but isolating the lean, contractile tissue component. Because it's normalized to height, it allows comparison of muscularity between people of different statures in a way that raw muscle mass in kilograms cannot, and it's conceptually related to research metrics like the Skeletal Muscle Mass Index (SMI) used in sarcopenia research, which similarly divides skeletal muscle mass by height squared to screen for age-related muscle loss.

Strength coaches, bodybuilders, and clinicians assessing sarcopenia (age-related muscle wasting) risk in older adults use a muscle-mass-relative-to-height metric like this because raw muscle mass alone is misleading — a tall and a short person can carry the same kilograms of muscle yet have very different proportional muscularity, and screening for low relative muscle mass is one component of frailty and sarcopenia risk assessment in geriatric and sports-medicine settings.

This calculator takes your muscle mass, height, and sex, and returns your muscle mass index along with where it falls — low, normal, or high — for your sex-specific reference range.