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Body Fat Calculator (Navy Method)

Estimate body fat percentage from circumference measurements using the U.S. Navy method.

How this calculator works

Enter your height and circumference measurements (neck, waist, and, for women, hip), and this calculator applies the U.S. Navy body fat formula, developed by Hodgdon and Beckett for military fitness assessment, to estimate your body fat percentage and category.

The formula

Men:   bodyFat% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: bodyFat% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387

(all measurements in inches)

Worked example

A man with a 70-inch height, 15-inch neck, and 34-inch waist:

  • bodyFat% = 86.010 × log10(19) − 70.041 × log10(70) + 36.76 = 17.5%
  • That falls in the “Average” category per the ACE bands (18-24% for men)

Frequently asked questions (FAQ)

How accurate is the Navy body fat method?

It's typically within a few percentage points of more precise methods like DEXA scans or hydrostatic weighing for most body types, which is quite good for a tape-measure-only method. It can be less accurate for people with atypical body compositions, like bodybuilders or very lean athletes.

Why does the formula use height and circumferences instead of skinfold calipers?

The Navy method was designed to be quick and require no special equipment beyond a measuring tape, useful for large-scale military fitness testing. Skinfold calipers can be more accurate in trained hands, but require training and equipment this method doesn't need.

What if my waist measurement is smaller than my neck?

That combination isn't physically typical and would make the formula's math invalid (it involves taking the logarithm of a negative or zero number), so this calculator shows a validation message instead of a nonsensical result. Double-check your measurements: waist should be measured at the navel, neck just below the larynx.

What do the ACE body fat categories mean?

The American Council on Exercise categorizes body fat into ranges: essential fat (the minimum needed for health), athletes, fitness, average, and obese. Thresholds differ for men and women, since women naturally carry more essential fat.

Can I use this method to track progress over time?

Yes. Since it only needs a tape measure, it's easy to repeat consistently. Measure at the same time of day, in the same spots, for the most comparable results over time.

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