Body Mass Calculator
Estimate fat mass and lean body mass from your weight and body fat percentage. Informational only, not medical advice.
Enter your estimated body fat percentage. Both very low and very high values may be unrealistic depending on context.
Privacy: runs locally in your browser. No values are stored or transmitted.
How it works
Fat mass is estimated as body weight × body fat fraction. Lean body mass is estimated as body weight − fat mass.
Examples
- 70 kg at 20% body fat → fat mass ≈ 14 kg, lean body mass ≈ 56 kg
- 154 lb at 18% body fat → fat mass ≈ 27.72 lb, lean body mass ≈ 126.28 lb
- Useful for simple body composition tracking, not diagnosis
FAQ
- What does this calculator do?
It estimates fat mass and lean body mass from your body weight and body fat percentage.
- What is fat mass?
Fat mass is the portion of total body weight that comes from body fat.
- What is lean body mass?
Lean body mass includes muscle, bone, organs, body water, and other non-fat tissue.
- Are the results exact?
No. Results are estimates and depend on how accurately body fat percentage was measured.
- Is my data stored?
No. All calculations run locally in your browser and are not stored or transmitted.