Body Fat Percentage Calculator
The US Navy tape method — body fat percentage from a few measurements with a tape measure.
This is the circumference method the US Navy has used for decades. All it needs is a flexible tape measure. It is not as accurate as a DEXA scan, but it is free, repeatable, and much more informative than BMI about what your weight is actually made of.
How this is worked out
The Navy equations use the logarithm of a circumference difference against the logarithm of height: waist minus neck for men, waist plus hip minus neck for women. Because they never look at your weight, two people of the same height and girth get the same percentage regardless of how heavy they are — which is the method's main weakness.
Expect roughly ±3 to 4 percentage points against a DEXA scan. That is fine for tracking a direction over months, provided you measure at the same time of day, on the same spots, with the same tape. Chasing a single reading is pointless; the trend is the signal.
For reference, the American Council on Exercise describes 2–5% (men) and 10–13% (women) as essential fat, 6–13% and 14–20% as athletic, 14–17% and 21–24% as fit, 18–24% and 25–31% as average, and above that as obese.
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Common questions
How accurate is the Navy tape method?
Within about three to four percentage points of a DEXA scan for most people, and less reliable at very high and very low body fat levels. Measurement technique matters more than the formula.
What is a healthy body fat percentage?
Broadly 14–24% for men and 21–31% for women, with athletes lower. Women need more essential fat than men for normal hormonal function, which is why the bands differ.