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Health & Fitnessbody composition

Lean Body Mass Calculator

Lean body mass and what it implies for protein and metabolic rate. Where body fat is known, lean mass follows directly; the formulas are estimates for when it is not.

Also called: lbm calculator, fat free mass.

cm
kg
Sex
%
Lean body mass
58.47

58.47 kg of lean mass and 19.53 kg of fat, by the Boer formula. That implies a protein target of about 117 g a day at 2 g per kg of lean mass, and a resting metabolic rate near 1,633 kcal. No body fat entered, so the Boer formula estimates from height and weight. Measuring body fat gives a better answer.

Fat mass
19.53
Daily protein target
117
Resting metabolic rate
1,633
Boer formula
58.47
Hume formula
54.42
Method used
Boer formula
On the methods
No body fat entered, so the Boer formula estimates from height and weight. Measuring body fat gives a better answer.
How this is calculated

For reference only. Verify against your clinical protocol before acting on this number.

Method and background

This is what the calculation gives for the numbers you entered. It is an estimate, not advice, and it knows nothing about your situation beyond those numbers. Rules for United States change on a published schedule; the effective date is shown on every rule-based tool.

How this is calculated

If you know your body fat percentage, lean mass is simply weight less fat, which needs no formula. The Boer and Hume equations estimate it from height and weight alone and are shown for comparison. Lean mass is the more useful basis for two things: protein targets, since fat mass has no protein requirement, and the Katch-McArdle metabolic rate equation, which uses lean mass and is more accurate than weight-based equations for anyone lean or unusually muscular.

measured body fat gives lean mass directly; the formulas estimate it where body fat is unknown
W
Weight

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

with a known body fat percentage

Height
172 cm
Weight
78 kg
Sex
Male
Body fat, if known
22 %
Protein target per kg of lean mass
2

Lean body mass60.84

78 x 0.78; 60.84 x 2

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without body fat the Boer formula is used

Height
172 cm
Weight
78 kg
Sex
Male
Body fat, if known
0 %
Protein target per kg of lean mass
2

Lean body mass58.47

boundary: 0.407 x 78 + 0.267 x 172 - 19.2

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Method and limits

What it assumes

  • Body fat measured or estimated reasonably, since everything follows from it.

What it deliberately does not model

  • The formulas estimate from height and weight and cannot distinguish body composition.
  • Protein recommendations vary with training status and goals; the default here suits resistance training.
  • Katch-McArdle is more accurate than weight-based equations only when lean mass is known accurately.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

Why base protein on lean mass?
Because fat mass has no protein requirement. Basing intake on total weight overstates the need for anyone carrying substantial fat mass.