HesapHanem

Muscle Mass Index Calculator

Enter your muscle mass, height and sex to get your muscle mass index.

How it is calculated

The index is SMI = skeletal muscle mass (kg) / height (m)². Height is entered in centimetres and converted to metres inside the tool; muscle mass is in kilograms. The result is in kg/m² with two decimals, and the category is applied to that rounded value. The bands are those of Janssen et al., American Journal of Epidemiology 2004. Men: 8.50 or less is Low (high risk), 8.51 to 10.75 Moderately low (moderate risk), above 10.75 Normal. Women: 5.75 or less is Low, 5.76 to 6.75 Moderately low, above 6.75 Normal. Anything other than “female” is treated as male. Both numbers must be above zero. The cut-offs were derived for older adults with skeletal muscle estimated by bioimpedance, so they are a screening aid for sarcopenia risk, not a diagnosis, and they do not fit figures from devices that report total muscle or lean mass.

Worked example

A man is 170 cm tall and a bioimpedance scan estimates 30 kg of skeletal muscle. Height in metres: 1.70, and 1.70² = 2.89. Index: 30 / 2.89 = 10.38 kg/m². For men that lies between 8.51 and 10.75, so the category is Moderately low (moderate risk). With 32 kg he would reach 11.07 kg/m², above 10.75, which is Normal. A woman of the same height with 18 kg has 6.23 kg/m², between 5.76 and 6.75, which is also moderately low for women.

Try this example →

Common mistakes

  • Entering body weight instead of skeletal muscle mass. That produces a BMI-style number far above any muscle band.
  • Entering the “muscle mass” of a home scale. Many scales report total muscle or lean mass, which is much larger than skeletal muscle mass, so the index lands in Normal even when skeletal muscle is low.
  • Entering height in metres. The field takes centimetres, so 1.70 is read as 1.7 cm and gives an enormous index.
  • Forgetting to set the sex. The bands differ: 6.6 kg/m² is moderately low for a woman but low for a man.
  • Reading Low as a diagnosis of sarcopenia. Sarcopenia also needs low strength or performance, assessed by a clinician.

Sources

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 divides your skeletal muscle mass by your height squared and places the result in the sex-specific bands of Janssen et al. (2004), who measured skeletal muscle by bioelectrical impedance in older adults and linked the index to physical disability: for men, 8.50 kg/m² or less is low (high risk) and 8.51–10.75 moderately low (moderate risk); for women, 5.75 or less is low and 5.76–6.75 moderately low; anything above is shown as normal. No source defines a “high” muscle band, so the tool has none. The bands assume skeletal muscle mass as estimated by bioimpedance; a body-composition scale that reports total “muscle mass” or lean mass gives a larger number that cannot be compared with them, and the cut-offs were set for older adults, not athletes.

Was this helpful?

You can pick up to 3 reactions.

Comments (1)

  • Editorial team

    The input is skeletal muscle mass in kilograms, a figure that normally comes from a body-composition scan, not from a bathroom scale. With the default 32 kg at 175 cm the index is 10.45 kg/m², which falls in the moderately low band for a man, and the band edge sits at 10.75. A result near an edge is borderline, since a small change in the input can flip the category. Which device or report did your muscle mass figure come from?

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Compound Interest Calculator

Calculate the final amount and interest earned with compounding.

All Calculators