Boer Formula Calculator (Lean Body Mass)

The Boer formula is two short linear equations, one per sex, with weight in kilograms and height in centimetres. For men it is LBM = 0.407 × weight + 0.267 × height − 19.2. For women it is LBM = 0.252 × weight + 0.473 × height − 48.3. That is the whole model — no squaring, no body-fat term, just a weighted sum of your height and weight with a sex-specific constant subtracted at the end. Work an example through the male equation for someone who is 80 kg and 178 cm: 0.407 × 80 = 32.56, 0.267 × 178 = 47.526, and 32.56 + 47.526 − 19.2 comes to about 60.9 kg of lean body mass. That is exactly the number the tool above returns for those inputs, and swapping in the female constants gives the equivalent estimate for a woman.

Boer is one of three classic lean-mass formulas, and it helps to know how it sits against the other two. The James (1976) formula uses a weight-over-height-squared term rather than a simple weighted sum, which pulls its estimate down for shorter or heavier builds. The Hume (1966) formula was derived from total-body-water measurements and is still used in pharmacology for drug dosing. For the same 80 kg, 178 cm man, the three land a few kilograms apart — Boer near 60.9 kg, James a little higher, Hume a little lower — because each was fitted to a different study population. None is “the truth”; they are three reasonable estimates of the same quantity. That is why the general Lean Body Mass Calculator shows all three plus their average side by side, and why a measured body fat percentage — which you can get from the Body Fat % Calculator — beats any of them when you have it.

Once you have a lean-mass figure, it becomes the input to more accurate metabolism maths. The Katch-McArdle Calculator works out your resting and daily calorie burn from lean body mass rather than total weight, which is the most accurate approach for lean, muscular bodies. And if you want to understand where the Boer estimate stops being muscle and starts including bone, organs and water, the Lean Body Mass vs Muscle Mass page breaks that down. To normalise the same lean-mass figure to your height, the FFMI Calculator divides it by height squared.