Body Fat Calculator
Estimate your body fat percentage from a few tape measurements, with the U.S. Navy equations and every step of the math shown.
Just below the Adam's apple, tape level all around.
Usually about halfway between the belly button and the bottom of the breastbone, after a normal breath out.
Around the widest part of the buttocks, seen from the side.
Add your weight to see pounds of fat
Estimated body fat
31%
From the U.S. Navy tape-measure equations (Hodgdon and Beckett, 1984), which the Department of Defense prescribed for all services in 2002.
| Waist plus hips minus neck | 56.5 in |
|---|---|
| 163.205 × log₁₀(56.5) | +285.94 |
| 97.684 × log₁₀(height 64 in) | −176.43 |
| Constant | −78.387 |
| Body fat | 31.1% |
| Rounded to a whole percent, as the military does | 31% |
A tape measure estimates body fat from your shape; it does not measure fat directly. To compare over time, measure the same spots the same way each time.
This is general information, not medical advice. Talk to a doctor about your own numbers.
How this is calculated
The equations come from J. A. Hodgdon and M. B. Beckett at the Naval Health Research Center in San Diego (1984), one for men and one for women. In 2002 the Department of Defense made them the body fat method for all services (DoD Instruction 1308.3), and the Army’s regulation AR 600-9 prints them with worked examples. All measurements are in inches; the calculator converts centimeters.
Men: body fat % = 86.010 × log₁₀(belly − neck) − 70.041 × log₁₀(height) + 36.76.
Women: body fat % = 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387.
Example for a woman from AR 600-9: neck 15, waist 42, hips 44, height 64 inches. 42 + 44 − 15 = 71. 163.205 × log₁₀(71) = 302.13; 97.684 × log₁₀(64) = 176.43. 302.13 − 176.43 − 78.387 = 47.3, rounded 47%. For a man: neck 16, belly 49, height 69: 86.010 × log₁₀(33) − 70.041 × log₁₀(69) + 36.76 = 38.6, rounded 39%. The Department of Defense rounds to whole percent because decimals would suggest more precision than a tape measure has.
How to measure
Use a tape that does not stretch, keep it level with the floor, snug against the skin without pressing in. Measure each spot three times and take the average. The Department of Defense describes the spots this way:
- Neck: just below the larynx (Adam’s apple), looking straight ahead, shoulders down.
- Men’s belly: at the navel, arms at the sides, at the end of a normal breath out.
- Women’s waist: at the narrowest point, usually halfway between the navel and the bottom of the breastbone, after a normal breath out.
- Women’s hips: over the widest part of the buttocks, seen from the side.
The military rounds the neck up and the belly, waist and hips down to the nearest half inch, which nudges the result a little lower.
Is my number good?
We do not label your result. The CDC’s adult weight categories use BMI, which does not separate fat from muscle and bone, and we did not find a body fat table from a U.S. health agency to check against. For reference only, these are the Army’s maximums for soldiers, a fitness standard and not a health category:
| Age | Men | Women |
|---|---|---|
| 17–20 | 20% | 30% |
| 21–27 | 22% | 32% |
| 28–39 | 24% | 34% |
| 40 and older | 26% | 36% |
What the military uses now
In June 2023 the Army switched to a tape test at one site, the belly at the navel, with body weight (Army Directive 2023-11). Its current worksheet, DA Form 5500 from July 2026, screens soldiers with the waist-to-height ratio instead: waist at the navel divided by height, where 0.550 or more does not meet the Army standard. This calculator keeps the two- and three-site Navy equations because they are published in full with worked examples.
Limits
A tape measure estimates body fat from your shape; it does not measure fat. The equations were developed for adult service members, so they are not for children or during pregnancy.
Sources
Checked against the sources below on .
- U.S. Army: AR 600-9, The Army Body Composition Program (July 16, 2019, change 1 of February 27, 2025), Table B-5 equations and sample calculations
- U.S. Army: DA Form 5500, Army Body Composition Screening and Assessment Worksheet (July 2026), waist-to-height ratio
- CDC: About Body Mass Index (December 16, 2025), BMI does not separate fat from muscle and bone
- U.S. Army: Army publishes new body fat assessment guidance (Army Directive 2023-11, June 12, 2023)
Questions people ask
How do I measure my body fat with a tape measure?
Measure your height, your neck just below the Adam's apple and your belly at the navel (men), or your neck, your waist at its narrowest and your hips at the widest part (women). Enter the averages of three tries.
What is the Navy body fat formula?
Men: 86.010 × log10(belly − neck) − 70.041 × log10(height) + 36.76. Women: 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387. All measurements in inches.
What body fat percentage is healthy?
There is no CDC table for body fat percentage; the CDC's adult categories use BMI. For comparison, the Army allows soldiers at most 20 to 26% for men and 30 to 36% for women, depending on age.
Does the Army still use the tape test?
Since July 2026 its worksheet screens with waist-to-height ratio: 0.550 or more does not meet the standard. From June 2023 the Army used a one-site tape at the navel, and before that the Navy equations on this page.
Is body fat percentage better than BMI?
They answer different questions. BMI uses only height and weight and does not separate fat from muscle and bone, the CDC says. A tape method estimates fat from your shape, but it is also an estimate.