Body Fat (US Navy) Calculator
The US Navy body fat method estimates body fat percentage from simple tape measurements rather than calipers or scales. For men it uses waist, neck and height; for women it adds the hip measurement. The method was developed for military body composition assessment because it needs only a measuring tape and gives a repeatable estimate. This calculator applies the standard Navy circumference equations to your figures and returns an estimated body fat percentage. For men the formula is 86.010 times the base-10 logarithm of waist minus neck, minus 70.041 times the log of height, plus 36.76, with all measurements in inches. Enter a 34 inch waist, a 16 inch neck and a height of 70 inches and the tool returns about 15.49 percent body fat. The estimate is most reliable when measurements are taken carefully at the right spots: the waist at the navel, the neck just below the larynx, and height standing straight. Because it is an estimate from tape measurements, treat the result as a guide and track changes over time rather than fixating on a single reading. The full formula and a worked example that reconciles exactly to the calculator appear below.
The US Navy method estimates body fat from tape measurements: for men, %BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. A 34 inch waist, 16 inch neck and 70 inch height give about 15.49% body fat.
US Navy body fat formula
Men: %BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
Women: %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387
all measurements in inches, log10 is base-10 logarithm
The relevant circumferences are combined inside a base-10 logarithm, scaled by published constants, and adjusted by a constant term. The result is an estimated body fat percentage.
Worked example
A man with a 34 inch waist, a 16 inch neck and a height of 70 inches.
- waist - neck = 34 - 16 = 18; log10(18) = 1.25527
- 86.010 x 1.25527 = 107.966
- log10(70) = 1.84510; 70.041 x 1.84510 = 129.233
- %BF = 107.966 - 129.233 + 36.76 = 15.49%
These are the calculator's default inputs, so the result above matches the widget exactly.
Body Fat (US Navy) Calculator: frequently asked questions
How accurate is the US Navy body fat method?
It is a tape-measure estimate, so it is less precise than methods like DEXA or hydrostatic weighing, but it is repeatable and needs no equipment beyond a tape. Accuracy depends on measuring at the correct sites. Use it to track trends rather than as a clinical figure.
Where do I measure for the Navy method?
Measure the neck just below the larynx, the waist at the navel for men, and for women the waist at the narrowest point plus the hips at the widest point. Stand relaxed and keep the tape level. Consistent placement matters more than a single perfect reading.
Why does the women's formula need a hip measurement?
Body fat distribution differs by sex, so the women's equation adds the hip circumference to capture that and uses its own constants. The men's formula relies on waist and neck alone. Selecting the correct sex in the calculator applies the matching equation.
What is a healthy body fat percentage?
Healthy ranges vary by age and sex. The US Centers for Disease Control and Prevention treats body composition as one of several health markers and emphasizes overall activity and diet rather than a single number. Discuss targets with a clinician.
Does the calculator store my measurements?
No. All arithmetic runs in your browser and nothing is sent to a server or saved. Refreshing the page resets the inputs to the defaults shown.
Official sources
- Physical activity and health guidance: US Centers for Disease Control and Prevention (CDC). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.