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Lean body mass calculator

Subtract the fat fraction from total mass using a body-fat percentage you supply.

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Lean body mass calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Answer

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Subtract the fat fraction from total mass using a body-fat percentage you supply.

More results
Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Step-by-step calculation
Inputs are substituted below. Each line evaluates the next operation; intermediate values are displayed to 12 significant digits while the calculation uses full precision.
    Saved scenario
    Save the current answer, then change an input to compare. This clears when you leave.
    Formula and assumptions
    Non-fat mass = total mass × (1 − fat percentage/100). The result inherits the uncertainty of the body-fat measurement. No body-fat prediction equation, target range, diagnosis or diet recommendation is supplied.
    Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
    Scratch calculator
    Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.
    Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.
    Links include your inputs and settings. Anyone with the link can see them, so leave out private text. Files and generated results are left out; random draws run again.
    Keyboard shortcuts
    Updated 
    Using Lean body mass calculator
    Subtract the fat fraction from total mass using a body-fat percentage you supply.
    Non-fat mass = total mass × (1 − fat percentage/100). The result inherits the uncertainty of the body-fat measurement. No body-fat prediction equation, target range, diagnosis or diet recommendation is supplied.
    Next: Calculate BMI
    A worked example
    Example inputs: total body mass = 80, measured body-fat percentage = 20. Mass excluding body fat = 64.
    Before you use the result
    Non-fat mass = total mass × (1 − fat percentage/100). The result inherits the uncertainty of the body-fat measurement. No body-fat prediction equation, target range, diagnosis or diet recommendation is supplied.
    Example results for total body mass
    These examples use Measured body-fat percentage: 20. They are reference calculations, not recommended settings.
    Total body massMass excluding body fat
    4032
    8064
    160128
    Cite this page
    ToolOctopus. “Lean body mass calculator.” Updated 2026-09-26. https://tooloctopus.com/lean-body-mass-calculator.
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