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Lean Body Mass Calculator

Enter your sex, age, height and weight to estimate lean body mass with the Boer formula. The result is shown in kilograms and pounds alongside the estimated fat mass, with the exact formula and converted values. For adults aged 18 and over. Calculated locally and never stored.

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1. About you

Adults 18+ · Boer formula

Imperial values are converted with 1 in = 2.54 cm and 1 lb = 0.45359237 kg.

2. Estimate

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Enter your details, then press Calculate lean body mass.
About this tool

About Lean Body Mass Calculator

Lean Body Mass Calculator estimates an adult's lean body mass — body weight minus fat — with the Boer formula, using only sex, height and weight. It shows lean body mass and the remaining estimated fat mass in both kilograms and pounds, together with the exact formula and the converted values used.

Lean body mass is used in some exercise, nutrition and dosing contexts because it reflects body composition rather than total weight. When a tape measure or scan is not available, a height-and-weight formula offers a quick, clearly explained estimate.

How to use

Step by step

  1. Choose metric or imperial units.
  2. Select your sex and enter your age (18 or over).
  3. Enter your height and weight.
  4. Press Calculate lean body mass.
  5. Review the lean and fat mass in kg and lb, the formula and the converted values, then copy or download the summary.
Key features

What it offers

  • Boer formula for adult males and females
  • Lean body mass and estimated fat mass in kilograms and pounds
  • Exact formula with converted centimetre and kilogram values shown
  • Metric or imperial input
  • Plausibility checks on height, weight and the formula result
  • No categories, health labels or diagnostic statements
Best practices

Tips for best results

  • Measure height without shoes and weigh yourself at a consistent time of day.
  • Compare results over time using the same method.
  • Expect formula estimates to differ from scans, especially for very muscular people.
  • Use the Body Fat Calculator for a tape-measure-based comparison.
Benefits

Why people use it

Quick

Needs only sex, height and weight.

Clear

Formula and conversions are shown in full.

Private

Calculated locally and never stored.

FAQ

Common questions

Lean body mass is an estimate of everything in the body except stored fat — muscle, bone, organs, skin and body water. Fat mass is the difference between total body weight and lean body mass.
The Boer formula (1984). With weight in kilograms and height in centimetres: males LBM = 0.407 × weight + 0.267 × height − 19.2; females LBM = 0.252 × weight + 0.473 × height − 48.3. Estimated fat mass = weight − LBM.
The Boer formula was developed for adults, so the calculator only shows results for people aged 18 and over. Age is not otherwise used in the formula.
Yes. Choose Imperial to enter height in feet and inches and weight in pounds. They are converted with 1 in = 2.54 cm and 1 lb = 0.45359237 kg before the formula is applied, and the converted values are shown in the result.
Height and weight must each be within plausible adult ranges, and the formula must produce a lean mass that is greater than zero and less than total body weight. Combinations outside that range would not give a meaningful estimate, so the calculator asks you to check the values.
No. The calculator does not assign categories or health labels. Formula-based estimates can differ from measured body composition, especially for very muscular people. This is a general educational estimate, not medical advice, diagnosis or treatment.
The Body Fat Calculator uses tape-measure circumferences with the US Navy method. This calculator uses only sex, height and weight with the Boer formula, so the two methods can give different results.
No. The calculation runs entirely in your browser and nothing is stored.

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Private by design

This runs entirely in your browser

No file or text you enter here is uploaded. Encoding and decoding happen on your device using native browser APIs — close the tab and nothing remains on a server.

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