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Body Composition

Lean Body Mass Calculator

Estimate your lean body mass — everything except body fat — from weight, height and gender using the Boer formula.

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Why Use This Calculator?

  • ✓Uses the widely referenced Boer formula.
  • ✓Shows lean mass, fat mass and lean mass percentage.
  • ✓Supports metric (kg/cm) and imperial (lb/ft-in) units.

On This Page

Lean Body Mass Calculator Formula Quick Reference Key Terms Explained Where It's Used Worked Examples Tips & Mistakes FAQs

Lean Body Mass Calculator

About Lean Body Mass Calculator

Lean body mass (LBM) is your total body weight minus fat mass — it includes muscle, bone, organs and water. It's a more stable reference point than total weight for tracking training progress, and is often used as a base for protein-intake and medication-dosing estimates.

Results

Lean Body Mass
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Fat Mass
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Lean Mass % of Total Weight
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Summary

Enter values to see your results.

Lean Body Mass Calculator Formula

Boer Formula (Men)

LBM = 0.407 × Weight(kg) + 0.267 × Height(cm) − 19.2

Boer Formula (Women)

LBM = 0.252 × Weight(kg) + 0.473 × Height(cm) − 48.3

Fat Mass

Fat Mass = Total Weight − Lean Body Mass

Lean Mass %

Lean Mass % = (LBM ÷ Total Weight) × 100

Quick Reference

FormulaBasisCommon Use
BoerWeight + heightGeneral population, used here
JamesWeight + heightAlternative, tends to differ at extremes of weight
HumeWeight + heightOften used in clinical dosing contexts

Why Formulas Differ Slightly

Each formula was derived from a different reference population, so results can vary by a kilogram or two.

Important Note

These are population-based estimates. DEXA scans or hydrostatic weighing give a directly measured, more accurate figure.

Key Terms Explained

Total body weight is made up of lean tissue and fat. Separating the two gives a clearer picture of body composition than weight alone.

💪 Lean Body Mass

  • Weight from muscle, bone, organs and water.
  • Excludes only body fat.
  • Tends to stay more stable than total weight day-to-day.

🧈 Fat Mass

  • Total weight minus lean body mass.
  • The component targeted during fat-loss phases.
  • Varies more than lean mass with diet and hydration.

📊 Body Composition

  • The ratio of lean mass to fat mass.
  • A more informative metric than weight or BMI alone.
  • Tracked over weeks/months, not day-to-day.

🧮 Boer Formula

  • A regression equation estimating LBM from weight, height and gender.
  • Published in 1984, still widely used.
  • Doesn't require calipers or a DEXA scan.

Where It's Used

🥩 Protein Intake Planning

Base daily protein targets on lean mass rather than total weight.

💊 Medication Dosing Reference

Some clinical dosing guidelines reference lean body mass (consult a professional).

📈 Training Progress Tracking

See if weight change is coming from muscle or fat.

🥗 Macro Calculations

Feed lean mass into calorie and macro calculators for more accurate targets.

🏋️ Body Recomposition

Track whether a cut or bulk is preserving lean tissue.

🥊 Weight-Class Planning

Athletes in weight-class sports use LBM to plan safe cutting margins.

Worked Examples

Example 1 — Male

70 kg, 175 cm → LBM ≈ 56.6 kg, fat mass ≈ 13.4 kg (81% lean).

Example 2 — Female

60 kg, 165 cm → LBM ≈ 45.1 kg, fat mass ≈ 14.9 kg (75% lean).

Example 3 — Imperial Input

154 lb (≈70 kg), 5'9" (175 cm) male → same result as Example 1, ≈124.7 lb lean mass.

Best Practices & Common Mistakes

✅ Best Practices

  • Re-measure weight under consistent conditions (same time of day, similar hydration).
  • Track lean mass trend over weeks, not single readings.
  • Use lean mass to set protein targets, especially during fat loss.
  • Cross-check with a DEXA scan periodically if precision matters.
  • Use the same formula consistently rather than switching between Boer/James/Hume.

❌ Common Mistakes

  • Treating the estimate as a precise clinical measurement.
  • Comparing LBM across different formulas as if they're interchangeable.
  • Ignoring hydration swings, which affect weight but not true lean tissue.
  • Using LBM formulas for children or non-adult body types (not validated for these groups).
  • Forgetting to switch units correctly between metric and imperial.

Frequently Asked Questions

It's a reasonably good population-level estimate, typically within a few kilograms of DEXA-measured lean mass, but individual accuracy varies.
Lean body mass includes muscle plus bone, organs, and body water — it's a broader category than muscle mass alone.
Many nutrition coaches recommend basing protein targets on lean mass, since fat tissue requires comparatively little protein to maintain.
No — the Boer formula was derived from adult data and isn't validated for pediatric body composition.

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