Why is there no Boer or Hume estimate option?

This canonical tool uses only a body-fat percentage you supply. Demographic equations estimate different compartments and can obscure method uncertainty.

Which body-fat method should I use?

Use a method appropriate to your purpose and interpret it with its known uncertainty. For tracking, consistency of device and protocol is important.

Can I compare a DXA result with a smart scale?

Direct comparison can be misleading because methods estimate body compartments differently.

Does this diagnose low muscle mass?

No. It neither measures skeletal muscle nor applies clinical criteria.

Lean Body Mass from Measured Body Fat

Use your weight and an existing body-fat measurement—without substituting a muscle-mass formula.

No hidden prediction equation

Kilograms or pounds

Fat and lean mass breakdown

Unit system

KilogramsPounds

Body weightEnter weight in the selected unit.Measured body-fat percentageUse a result from a stated measurement method; this calculator does not infer body fat from sex, height, or age.

How to Calculate Lean Body Mass

This method intentionally requires a body-fat percentage rather than guessing from demographics.

Select kilograms or pounds.

Record the method

Hydration, device, protocol, and timing can shift body-fat estimates. Keep those details when tracking change.

Weight Minus Estimated Fat Mass

The result is the non-fat remainder in a two-compartment calculation. Body-composition literature uses lean body mass, lean soft tissue, and fat-free mass inconsistently, so the page states exactly what is calculated. Skeletal muscle is only one component and has its own canonical calculator.

Lean Mass Examples

Metric example

Weight and measured body fat

weight:80

bodyFatPercent:20

Estimated lean body mass

64.0 kg lean body mass; 16.0 kg fat mass

80 × 0.20 = 16 kg fat mass; 80 − 16 = 64 kg.

Imperial example

Weight and measured body fat

weight:200

bodyFatPercent:25

Estimated lean body mass

150.0 lb lean body mass; 50.0 lb fat mass

The percentage arithmetic works directly in pounds.

Measurement error carries through

A one-percentage-point change in entered body fat changes estimated lean mass by one percent of body weight.

Frequently Asked Questions

No. This lean remainder includes more than skeletal muscle, such as organs, water, connective tissue, and bone-related components depending on the measurement model.

Still have questions about this calculation?

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Measured-Percentage Formula

No demographic estimation method is included because this calculator's intent is arithmetic from a supplied measurement.

Formula

fat mass = weight × body-fat % / 100

Fat mass

fat mass = weight × body-fat % / 100

Lean body mass estimate

lean body mass = weight − fat mass

Scientific Background

NIH-indexed body-composition research documents inconsistent terminology and method-specific compartments. The calculator therefore reports a transparent two-compartment remainder and labels its limitations.