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
When to use this tool
This tool is designed for quick, practical tasks such as everyday calculations, data formatting, or simple conversions. It is best used when you need fast results without installing software or using complex tools.
When to use
- Quick checks or one-time calculations
- Validating or converting data before using it elsewhere
- Simple tasks that do not require advanced software
When not to use
- Critical financial, legal, or medical decisions
- Large-scale or automated processing
- Situations requiring guaranteed precision beyond basic validation
Always review results before using them in important contexts.
About this tool
This tool helps you perform quick utility operations directly in your browser. It runs entirely in your browser without sending data to a server.
You can use this tool when handling simple tasks without installing additional software. The results should be interpreted as a processed output based on your input data.
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.