Formula and calculation method
Lean body mass = body weight × (1 − body fat fraction).
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
How to use lean body mass calculator
- Set Measurement system by choosing the option that matches your calculation.
- Set Weight (kg or lb). The example below uses 70.
- Set Measured or estimated body fat (%). The example below uses 20.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Measurement system
- Metric (kg, cm)
- Weight (kg or lb)
- 70
- Measured or estimated body fat (%)
- 20
- Lean body mass (kg)
- 56
- Fat mass (kg)
- 14
Factors affecting your result
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Changing measurement system changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the lean body mass calculator work?
Lean body mass = body weight × (1 − body fat fraction).
What inputs does Lean Body Mass Calculator need?
Enter measurement system, weight (kg or lb), measured or estimated body fat (%). Read the unit labels; percentages are entered as ordinary percentages, not decimal fractions.
How should I interpret the lean body mass calculator result?
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Are my lean body mass calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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