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Skeletal Muscle Mass Estimate Calculator

Enter your weight, height, age and sex to estimate skeletal muscle mass.

How it is calculated

The tool uses a regression equation of the Lee type: SMM = 0.244 × W + 7.80 × H − 0.098 × age + S − 3.3, where W is body weight in kg, H is height in metres (your cm entry divided by 100), age is in years, and S is 6.6 for males and 0 for females. If the sex is not given, male is assumed. SMM is the estimated skeletal muscle mass in kg. It also shows SMM / W × 100 as a percentage of body weight and the skeletal muscle index SMM / H² in kg/m². There is no ethnicity term. The result is an estimate from measurements, not a scan, and no result is shown if it comes out non-positive or above body weight.

Worked example

A man weighs 75 kg, is 178 cm (1.78 m) tall and 35 years old. The weight term is 0.244 × 75 = 18.30. The height term is 7.80 × 1.78 = 13.88. Age subtracts 0.098 × 35 = 3.43. Adding the male constant 6.6 and subtracting 3.3 gives 18.30 + 13.88 − 3.43 + 6.6 − 3.3 = 32.05 kg. As a share of body weight that is 32.05 / 75 = 42.74%, and the index is 32.05 / 1.78² = 10.12 kg/m².

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Common mistakes

  • Entering the height in metres or in feet. The height field is in centimetres, so 1.78 m must be typed as 178.
  • Entering weight in pounds. The field is in kilograms, and a pound value gives a result that is far too high.
  • Forgetting to set the sex. With nothing selected the tool assumes male, which adds 6.6 kg to a woman's estimate.
  • Treating the figure as a measurement. It is a prediction from four numbers, and two people of the same size and age get the same result whatever their training, so it does not replace a DEXA or impedance scan.
  • Using it for children or for athletes with unusual builds. The tool accepts any positive age but the equation does not adapt to them.

Sources

About this calculator

Skeletal muscle mass — the muscle attached to bone that drives voluntary movement — can be estimated from simple anthropometric data (height, weight, age and sex) using regression equations validated against gold-standard methods like DEXA scanning or bioelectrical impedance analysis (BIA), such as the widely cited Lee et al. (2000) prediction equation.

These anthropometric estimates matter clinically because low skeletal muscle mass relative to body size is a defining feature of sarcopenia, the age-related loss of muscle mass and strength linked to falls, frailty and reduced independence in older adults, and tracking it over time is also common in strength training and body-composition monitoring when access to a DEXA scanner or BIA device is limited.

This calculator estimates your skeletal muscle mass in kilograms and as a percentage of body weight from your weight, height, age and sex, giving a reasonable estimate when direct body-composition testing is not available.

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