🏋️ Body Fat Percentage Calculator
Estimate body fat percentage and lean body mass using US Navy measurements.
Try the calculator
The values below are a working example. Change any field to recalculate instantly in your browser.
This estimate is not a substitute for clinical measurement.
Formula & Mathematical Logic
Body Fat % = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76
Computes exact mathematical outputs locally on your device with 0 network latency.
Step-by-Step Worked Example
Sample Scenario
A male with 85 cm waist, 38 cm neck, and 175 cm height has an estimated body fat of ~16.5%.
Frequently Asked Questions (FAQ)
How does the Body Fat Percentage Calculator work?
The Body Fat Percentage Calculator applies the mathematical formula Body Fat % = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76 to compute your inputs 100% locally in your web browser.
Is my personal or financial data private?
Yes. Calcixa operates on a 100% privacy-first zero-backend architecture. No data leaves your device.
CALCIXA PRACTICAL GUIDE
How to use the Body Fat Percentage Calculator
The body-fat calculator estimates percentage body fat from circumference measurements using the selected formula. Circumference methods are inexpensive and repeatable, but they are indirect estimates rather than a scan or laboratory measurement.
Tape placement, posture, breathing, hydration, and body shape can materially affect the result. For tracking, use the same tape, anatomical landmarks, time of day, and measurement technique each time.
Step-by-step
- Select the formula inputs and unit system shown by the calculator.
- Measure each circumference with a level, snug tape that does not compress skin.
- Repeat each measurement and use a consistent value.
- Calculate and interpret the estimate as a trend alongside other health information.
How to read the result
- Estimated body-fat percentage is derived from body circumferences and height.
- Lean mass is body weight minus the estimated fat mass.
- The displayed classification is descriptive and not a medical diagnosis.
Common mistakes to avoid
- Changing tape position between measurements.
- Comparing results produced by different formulas as if they were identical.
- Treating a single estimate as precise enough for medical decisions.
Important: This educational estimate is not medical advice or a diagnosis.
More questions about Body Fat Percentage Calculator
Why can a scan give a different result?
Circumference equations, skinfolds, bioimpedance, DEXA, and other methods use different assumptions and all have uncertainty.
When should I measure?
Use similar conditions each time, such as the same time of day and hydration state.
Does the calculator store my measurements?
No. The calculation runs in the browser and Calcixa does not receive the entered measurements.
Sources and methodology
Calcixa explains the model, assumptions, and limitations so you can verify the result. See our calculation and tool methodology for rounding, privacy, testing, and correction practices.
Maintained by the Calcixa product team. This page was last updated on 7 September 2026.