Lean body mass, women (Boer)

The formula

• LBM = 0.252 · m + 0.473 · h − 48.3

m is the weight in kilograms, h the height in centimetres and LBM the lean body mass in kilograms: everything that is not fat. Boer fitted the coefficients in 1984; the source is cited under the formula, and the version for men is on its own page.

Holds when the body is of ordinary build. The equation returns the average lean mass of women with that weight and height; it does not measure anyone, and a trained athlete is under-counted by it.

A worked example

60 kg and 165 cm: LBM = 0.252 · 60 + 0.473 · 165 − 48.3 = 15.12 + 78.05 − 48.3 = 44.9 kg. The remaining 15.1 kg, 25% of the weight, is the fat mass the estimate implies.

Why the coefficients differ from the men’s

Of each extra kilogram at the same height, the women’s equation counts 0.252 kg as lean against 0.407 in the men’s: on average a larger share of added weight is fat. The height term is larger, 0.473 against 0.267, and the constant correspondingly more negative, because the fit runs through a different range of heights and weights. The two equations are not one formula with a switch; each was fitted to its own group.

Lean mass and body fat

Fat = weight − LBM, and the body fat percentage is that fat over the weight: 25% in the example. The body fat percentage page estimates the same split from circumferences, and the two methods agree on average and not for every person.

Common mistakes

• Using the women’s coefficients for a man, or the other way round.
• Height in metres. The coefficients belong to centimetres.
• Reading the fat mass as a verdict. It is an average for the measurements, not a reading of the body.

Frequently asked questions