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Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — no scale or calipers required. Free, private, and instant.
Body Fat Calculator estimates body fat percentage using the U.S. Navy circumference method, from height, neck, waist, and (for women) hip measurements. Shows the result against standard body fat categories, plus estimated fat mass and lean mass in kilograms or pounds. Supports metric and imperial units. A population-level estimate, not medical advice. Calculations run entirely in your browser — no uploads, no signup. Built by FreeToolHub.
Your Measurements
100% client-side. Your data stays in your browser.
Unit System
Height
Hip measurement is used for the women's formula.
Results
How This Is Calculated
Formula Used
U.S. Navy (men): BF% = 495 / (1.0324 − 0.19077×log10(waist−neck) + 0.15456×log10(height)) − 450
This is a general population-level estimate based on a standard formula. It does not account for individual frame size, muscle distribution, or other factors. This tool does not provide medical advice.
Body Fat Categories (American Council on Exercise)
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Quick Examples
Estimate your body fat percentage instantly from a few tape-measure readings — no scale or calipers needed.
Frequently Asked Questions
What is the U.S. Navy body fat method?
The U.S. Navy method estimates body fat percentage from simple tape-measure circumferences — neck and waist for men, plus hip for women — combined with height. It was developed by the U.S. Navy as a fast, equipment-free alternative to skinfold calipers or underwater weighing, and remains one of the most widely used circumference-based estimation methods.
How do I measure my neck, waist, and hip correctly?
Measure neck just below the larynx (Adam's apple), waist at the navel while relaxed (not sucked in), and hip at its widest point. Keep the tape snug but not compressing the skin, measure standing up, and take each measurement two or three times to average out small errors.
What is a healthy body fat percentage?
Using the American Council on Exercise categories, average body fat is roughly 18-24% for men and 25-31% for women, while the fitness range is about 14-17% for men and 21-24% for women. Athletes typically sit lower still. These ranges are general guidelines, not individual health targets.
How accurate is this method?
The Navy method is a population-level estimate with a typical error margin of around 3-4 percentage points compared to lab methods like DEXA scans or hydrostatic weighing. It is accurate enough to track trends over time but should not be treated as a precise medical measurement.
Does this tool store my measurements?
No. All calculations run entirely in your browser using JavaScript. Nothing you enter is sent to a server, logged, or stored.
Is this medical advice?
No. This tool provides a general population-level estimate based on a standard formula. Individual body composition varies with frame size, muscle distribution, and other factors. Consult a doctor or qualified professional for a clinical body composition assessment.