TOOLOG TOOL
Body Fat Calculator | Calculate Body Fat, Fat Mass, and Lean Mass
Use this body fat calculator with height, neck, waist, weight, and female hip measurement to estimate body fat percentage, fat mass, and lean mass with the U.S. Navy formula and safer range checks.
Enter your measurements to estimate body fat using the U.S. Navy formula.
Supported ranges: height 120-230cm, neck 20-70cm, waist 40-180cm, hip 50-200cm, weight 30-250kg. Results are estimates, not medical diagnosis.
Estimate body fat in seconds
Body weight alone does not show how much is fat vs lean mass. This tool uses the U.S. Navy method to estimate:
- Body fat percentage
- Fat mass (kg)
- Lean mass (kg)
Use it when you need a quick body fat calculator, U.S. Navy body fat estimate, body fat percentage calculator, or fat mass and lean mass reference before comparing diet or training changes.
Key features
- Sex-specific U.S. Navy formula
- Body fat percentage, fat mass, and lean mass in one result
- Category label for quick interpretation
- Empty-state, out-of-range, and formula-validity checks
- Example input, result copying, and mobile-friendly controls
How to Use
- Choose sex.
- Enter height, neck, waist, and weight.
- In female mode, enter hip circumference too.
- Use the example button to preview the flow, then review body fat percentage, fat mass, and lean mass from your own measurements.
- Copy the result if you want to paste it into a workout log, diet note, or health tracker.
When Input Is Rejected
- Height outside 120-230cm, neck outside 20-70cm, waist outside 40-180cm, hip outside 50-200cm, or weight outside 30-250kg
- Male mode where waist is not larger than neck
- Female mode where waist + hip is not larger than neck
- Empty, non-number, or abnormally large pasted values
The tool blocks these cases instead of forcing a result because the U.S. Navy formula uses logarithms and needs valid measurement relationships.
Example and interpretation
The example button loads a female sample: height 165cm, neck 32cm, waist 95cm, hip 108cm, and weight 65kg. It lets you see how the calculation flow works before entering your own measurements.
The body fat percentage is a practical estimate, not a medical diagnosis. Tape position can change the output, so use the result for trend tracking. Measure at the same time of day, in the same posture, and under similar conditions.
Body weight can go down while body fat percentage goes up if lean mass drops faster than fat mass. For that reason, compare body fat percentage, fat mass, and lean mass together instead of relying on one number.
Related tools
FAQ
Why is hip circumference required in female mode?
The U.S. Navy formula for females uses waist + hip - neck measurements.
Is this result a medical diagnosis?
No. It is an estimate based on home measurements. Use it as a trend reference, and rely on a professional assessment or precise measurement test when accuracy matters.
Can body fat percentage go up while body weight goes down?
Yes. If lean mass drops faster than fat mass, the percentage can rise even when body weight decreases.
Why do I see an input error?
The formula needs valid measurement relationships. In male mode, waist must be larger than neck. In female mode, waist + hip must be larger than neck.
Summary
This body fat calculator helps you look beyond scale weight and check body composition changes with a U.S. Navy formula estimate.