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Fat-Free and Fat Mass Estimate — result sheet
Split adult body weight into estimated fat mass and fat-free mass using a supplied body-fat percentage, without mislabeling all fat-free tissue as muscle.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Fat mass = weight x bodyFatPercent / 100; fat-free mass = weight - fat mass.
A two-compartment model divides measured weight into fat and everything else. Fat-free mass includes water, bones, organs, and muscle, and is not strictly identical to lean body mass. Errors in the supplied body-fat percentage directly affect both estimates; the result does not diagnose nutritional or health status.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Age — years; Adult-only estimate; age checks scope rather than changing the subtraction.; minimum 18; maximum 100
- Weight — kg; minimum 25; maximum 350
- Supplied body-fat measurement — %; Use an existing measurement. This calculator does not measure or infer body-fat percentage.; minimum 0.1; maximum 70
Worked example
| Input | Value |
|---|---|
| Age | 32 |
| Weight | 76 |
| Supplied body-fat measurement | 18 |
Estimated fat-free mass: 62.32 kg; estimated fat mass: 13.68 kg.
Assumptions and limits
- Adult-only two-compartment estimate using a body-fat percentage measured elsewhere; it is not a new body composition measurement or diagnosis.
- Fat-free mass is not muscle mass and is not strictly identical to lean body mass; water, bone, and organs are included.
- Weight and body-fat percentage should refer to the same assessment. Hydration, measurement method, and measurement error limit interpretation; no treatment or body-fat target is provided.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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