The Boer formula
Men: LBM = 0.407 × weight (kg) + 0.267 × height (cm) − 19.2. Women: LBM = 0.252 × weight (kg) + 0.473 × height (cm) − 48.3. It was built for medical use and is often preferred for dosing contrast in CT scans. Like all height-and-weight formulas, it assumes an average build: very muscular people will be underestimated.
If you have a body fat estimate from the tape-measure calculator, a scan or calipers, the result above switches to weight × (1 − body fat %), which reflects your own composition.
What to do with the number
Lean mass feeds the Katch-McArdle equation on the BMR calculator. Tracked over time, it shows whether weight loss is coming from fat or from muscle. A drop in lean mass during a diet is a signal to increase protein and add resistance exercise.
Questions people ask
What is lean body mass?
Lean body mass is everything in your body except fat: muscle, bone, organs, skin, blood and water. It is usually 60–90% of body weight.
How is lean body mass calculated?
Without a scan, it is estimated from height and weight with formulas such as Boer (1984), or from a body fat percentage: lean mass = weight × (1 − body fat %). DEXA scans measure it directly.
Is lean body mass the same as muscle mass?
No. Skeletal muscle is typically around half of lean mass; the rest is bone, organs and water. So a 60 kg lean mass does not mean 60 kg of muscle.
Why does lean body mass matter?
It drives how many calories you burn at rest, and clinicians use it to dose some medicines and CT contrast. Keeping it up while losing weight, through protein and resistance training, is a common goal.
Sources
- Boer P. (1984). Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol 247:F632–F636.
- Caruso D et al. (2018). Lean body weight-tailored iodinated contrast injection in obese patients: Boer versus James formula. BioMed Res Int.
Every formula on VitalMetrics is listed with its original reference on Sources & methods.