Lean Body Mass Calculator
Lean body mass (LBM) represents everything in your body except fat — muscle, bone, organs, and water. The Boer formula provides an accurate estimate using weight, height, and sex, making it useful for setting protein targets and calibrating medication doses.
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Formula
Male LBM = 0.407W + 0.267H − 19.2; Female LBM = 0.252W + 0.473H − 48.3
The Boer formula uses weight (W in kg) and height (H in cm) with gender-specific coefficients derived from regression analysis of body composition data. Males have higher coefficients for weight because they carry more muscle relative to fat at any given weight, while females have a higher coefficient for height reflecting their proportionally longer limbs relative to torso mass.
How to use the Lean Body Mass Calculator
- 1
Enter your body weight
Value should be in kg.
- 2
Enter your height
Value should be in cm.
- 3
Enter your gender
- 4
Read your results instantly
Results update in real time as you type.
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Why lean body mass matters
Lean body mass is the metabolically active component of your body. Your basal metabolic rate is largely determined by LBM — muscle tissue burns far more calories at rest than fat tissue. Knowing your LBM allows more precise protein intake recommendations (based on lean mass rather than total weight), more accurate BMR calculations, and better tracking of body composition changes during recomposition programs where weight might stay stable while fat is replaced by muscle.
LBM versus fat-free mass
Lean body mass and fat-free mass are often used interchangeably but are technically different. Fat-free mass excludes all fat, including essential fat in the brain, nerves, and cell membranes. LBM includes a small amount of essential fat (roughly 3% in men and 12% in women) needed for physiological function. For most practical purposes — protein dosing, metabolic rate estimation, and fitness tracking — the difference is minor and the terms can be treated as equivalent.
Tips & Insights
Use LBM for protein targets
Setting protein intake at 1 g per pound of LBM is more precise than using total body weight, especially for heavier individuals where a significant portion of body weight is fat.
Track LBM changes over time
During a recomposition phase, total body weight may barely change while LBM increases and fat decreases. Tracking LBM reveals progress that the scale hides.
Combine with body fat percentage
You can cross-check this result: if you know your body fat percentage, LBM = total weight × (1 − body fat%). The two values should be within a few kg of each other.
Worked Examples
75 kg male, 175 cm
LBM ≈ 57.8 kg (127.4 lbs)
62 kg female, 165 cm
LBM ≈ 46.8 kg (103.2 lbs)
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Frequently Asked Questions
Is the Boer formula accurate?
It is accurate to within 2–3 kg for most average-build adults when compared to gold-standard DEXA scans. Very muscular or very obese individuals may see larger deviations.
What is a healthy LBM percentage?
Healthy body fat is roughly 10–20% for men and 18–28% for women, implying LBM percentages of 72–90% and 72–82% respectively.
Does LBM decrease with age?
Yes. Sarcopenia — age-related muscle loss — typically begins in the mid-30s and accelerates after 60, reducing LBM by 1–2% per year if not countered by resistance training.
Can I increase my LBM?
Yes, through progressive resistance training and adequate protein intake. Beginners can gain 1–2 lbs of LBM per month; advanced lifters gain much more slowly.
How does hydration affect LBM estimates?
Formulas like Boer use body weight, which includes water. Dehydration can temporarily lower your estimated LBM. Weigh yourself consistently — same time of day, same hydration state — for comparable results.
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