Navy Body Fat Calculator
All you need is a tape measure. Enter your height, neck, waist and (for women) hips to estimate your body fat percentage.
This calculator gives general estimates for information only. It is not medical advice and does not replace a consultation with a doctor or other qualified health professional.
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The formula
Men: 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. Women: 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387 (all in inches).
How the method works
Fat tends to collect around the waist, while the neck reflects lean mass. The Navy formula uses the difference between them, along with height, to estimate body fat. For women, the hips are included as well.
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2 to 5% | 10 to 13% |
| Athletes | 6 to 13% | 14 to 20% |
| Fitness | 14 to 17% | 21 to 24% |
| Average | 18 to 24% | 25 to 31% |
| Obese | 25% and over | 32% and over |
Limitations
The tape method can be off for very muscular or very lean people and those with unusual body shapes. Treat the result as a guide, and watch the trend over several weeks.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Male; Age (years): 30; Height (cm): 180; Neck (cm): 38; Waist at navel (cm): 90 | Estimated body fat: 19.9% |
| Female; Age (years): 28; Height (cm): 165; Neck (cm): 32; Waist at navel (cm): 76; Hip at widest point (cm, women only): 98 | Estimated body fat: 29.7% |
| Male; Age (years): 40; Height (feet): 5; Height (inches): 10; Neck (in): 15.5; Waist at navel (in): 36 | Estimated body fat: 20.4% |
Navy Body Fat Calculator: frequently asked questions
How accurate is a tape measure estimate?
The Navy method is typically within 3 to 4 percentage points of a DEXA scan for most people. It is better for tracking change over time than for a single exact figure, so measure the same way each time.
Where exactly should I measure?
Neck just below the larynx, waist at the navel (relaxed, not sucked in), and hips at the widest point. Keep the tape snug but not tight, and measure three times to average.
Can I rely on this result as medical advice?
No. It is a general estimate for information only. It cannot replace a check-up, and your doctor can interpret the numbers for your own situation.
Is what I enter in this calculator saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this calculator free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026