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Lean Body Mass Calculator

Calculate your lean body mass (LBM) and fat mass using body fat percentage and the Boer formula.

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About this Calculator

Calculate your lean body mass (LBM) and fat mass using body fat percentage and the Boer formula.

Formula & Calculations

Formula

LBM = Weight × (1 - BF%/100) | Boer (Male): LBM = 0.407W + 0.267H - 19.2 | Boer (Female): LBM = 0.252W + 0.473H - 48.3
Where:
  • LBM=Lean Body Mass — total body weight minus fat mass (kg)
  • W=Weight in kilograms
  • H=Height in centimeters
  • BF%=Body fat percentage
  • FM=Fat Mass — weight × (BF% / 100)

Assumptions

  • The Boer formula estimates LBM independently of body fat percentage and may differ from the BF%-based method.
  • Body fat percentage should be obtained from a reliable source (calipers, DEXA, or bioelectrical impedance).
  • LBM includes muscle, bone, organs, water, and other non-fat tissues.

Calculation Examples

Example 1

Inputs:Weight: 80 kg, Body Fat: 20%
Result:LBM: 64.0 kg, Fat Mass: 16.0 kg (from BF%). Boer estimate: ~63.1 kg

Using body fat %: LBM = 80 × (1 - 0.20) = 64.0 kg. The Boer formula provides an independent estimate based on height and weight.

Example 2

Inputs:Female, Height: 165 cm, Weight: 60 kg, Body Fat: 25%
Result:LBM: 45.0 kg, Fat Mass: 15.0 kg (from BF%). Boer estimate: ~44.9 kg

Using body fat %: LBM = 60 × (1 - 0.25) = 45.0 kg. Boer formula: 0.252(60) + 0.473(165) - 48.3 ≈ 44.9 kg.

Frequently Asked Questions

What is a healthy lean body mass?

There is no single 'healthy' LBM because it depends on height, gender, and frame size. Generally, women should have at least 38-42 kg and men at least 54-60 kg of LBM for basic health. Athletes often carry significantly more.

Why do the two methods give different results?

The BF%-based method uses your actual body fat measurement, while the Boer formula is a population-average regression equation. Differences of 1-3 kg are normal. Use the BF%-based result if you have an accurate body fat measurement.

How can I increase my lean body mass?

Progressive resistance training (weight lifting) combined with adequate protein intake (1.6-2.2 g/kg) is the most effective way to increase LBM. Ensure you're in a slight caloric surplus and getting sufficient sleep for recovery.