Health & Medicine · Biometrics
Lean Body Mass Calculator
Calculate lean body mass using the Boer formula for males and females based on height and weight.
Calculator
Formula
W = body weight in kilograms; H = height in centimeters; LBM = lean body mass in kilograms.
Source: Boer P. (1984). Estimated lean body mass as an index for normalization of body fluid volumes in humans. American Journal of Physiology, 247(4), F632–F636.
How it works
This calculator uses the Boer formula (1984), one of the most widely validated anthropometric equations for estimating LBM. It uses body weight and height with sex-specific coefficients to produce an estimate of fat-free mass in kilograms.
Fat mass is then derived by subtracting LBM from total body weight, and body fat percentage is calculated as fat mass divided by total weight. Enter 1 for male or 0 for female in the sex field.
Worked example
Consider a male weighing 80 kg and 180 cm tall:
LBM = 0.407 × 80 + 0.267 × 180 − 19.2 = 32.56 + 48.06 − 19.2 = 61.42 kg
Fat Mass = 80 − 61.42 = 18.58 kg
Body Fat = (18.58 ÷ 80) × 100 = 23.2%
Limitations & notes
The Boer formula is an estimation and does not account for age, ethnicity, fitness level, or hydration status, which can all significantly affect body composition. For clinical or performance purposes, methods such as DEXA scanning or hydrostatic weighing provide more accurate measurements. This calculator should not be used as the sole basis for medical or nutritional decisions.
Frequently asked questions
What is lean body mass?
Lean body mass is total body weight minus fat mass, encompassing muscle, bone, water, and organs. It is sometimes used interchangeably with fat-free mass, though technically LBM retains a small amount of essential fat.
Which formula does this calculator use?
This calculator uses the Boer (1984) formula, which is widely used in pharmacokinetics and clinical medicine. It is derived from height and weight with separate equations for males and females.
Why does lean body mass matter for medication dosing?
Many drugs, especially those that do not distribute well into fat tissue, are dosed based on LBM rather than total body weight to avoid overdosing obese patients. Common examples include certain antibiotics and chemotherapy agents.
How accurate is the Boer formula?
The Boer formula performs well in average-weight adults but becomes less accurate at extremes of body composition such as severe obesity or very low body fat. DEXA or bioelectrical impedance analysis are more precise alternatives.
Can I use this calculator to track fitness progress?
You can use it to monitor trends in LBM over time as your weight and body composition change. However, because it relies only on weight and height, it cannot detect muscle gain while fat is lost if total weight stays the same.
Last updated: 2025-01-15 · Formula verified against primary sources.