Where to measure
The sites below are the ones used in the Navy study and written into the Department of Defense’s 2002 instruction on body fat measurement.
Men
- Neck: just below the larynx (Adam’s apple), with the tape as close to level as the neck allows and not over the Adam’s apple.
- Waist: around the abdomen at the level of the navel.
Women
- Neck: just below the larynx, as for men.
- Waist: the natural waist, at the narrowest point of the abdomen, usually about halfway between the navel and the lower end of the breastbone.
- Hips: over the greatest protrusion of the buttocks, seen from the side.
Technique
- Use a tape that does not stretch. Lay it against the skin so that it follows the body without pressing into it, and keep it level with the floor.
- Stand with arms at the sides, and read the waist at the end of a normal, relaxed breath out.
- Measure height without shoes.
- The instruction has each site measured three times, working through the whole set each time, and once more if one reading is over an inch away from the other two.
- For women, if the narrowest point of the waist is hard to see, the instruction says to measure at several likely places and use the smallest value.
Navy body fat chart
Body fat percentage by the 1984 equations. For men, subtract your neck from your waist, both in inches, find that number in the first column and read across to your height. For women, add waist and hips and subtract the neck.
Men
| Waist − neck | 5′4″ | 5′7″ | 5′10″ | 6′1″ | 6′4″ |
|---|---|---|---|---|---|
| 14 in | 9% | 8% | 7% | 5% | 4% |
| 15 in | 12% | 10% | 9% | 8% | 7% |
| 16 in | 14% | 13% | 11% | 10% | 9% |
| 17 in | 16% | 15% | 13% | 12% | 11% |
| 18 in | 18% | 17% | 15% | 14% | 13% |
| 19 in | 20% | 19% | 17% | 16% | 15% |
| 20 in | 22% | 21% | 19% | 18% | 17% |
| 21 in | 24% | 22% | 21% | 20% | 19% |
| 22 in | 26% | 24% | 23% | 22% | 20% |
| 23 in | 27% | 26% | 25% | 23% | 22% |
| 24 in | 29% | 27% | 26% | 25% | 24% |
| 25 in | 30% | 29% | 28% | 26% | 25% |
| 26 in | 32% | 31% | 29% | 28% | 27% |
| 27 in | 33% | 32% | 31% | 29% | 28% |
| 28 in | 35% | 33% | 32% | 31% | 29% |
| 29 in | 36% | 35% | 33% | 32% | 31% |
| 30 in | 38% | 36% | 35% | 33% | 32% |
Women
| Waist + hip − neck | 5′0″ | 5′3″ | 5′6″ | 5′9″ | 6′0″ |
|---|---|---|---|---|---|
| 46 in | 19% | 17% | 15% | 14% | 12% |
| 48 in | 22% | 20% | 18% | 16% | 15% |
| 50 in | 25% | 23% | 21% | 19% | 17% |
| 52 in | 28% | 26% | 24% | 22% | 20% |
| 54 in | 31% | 28% | 26% | 24% | 23% |
| 56 in | 33% | 31% | 29% | 27% | 25% |
| 58 in | 36% | 33% | 31% | 29% | 27% |
| 60 in | 38% | 36% | 34% | 32% | 30% |
| 62 in | 41% | 38% | 36% | 34% | 32% |
| 64 in | 43% | 41% | 38% | 36% | 34% |
| 66 in | 45% | 43% | 41% | 39% | 37% |
| 68 in | 47% | 45% | 43% | 41% | 39% |
| 70 in | 50% | 47% | 45% | 43% | 41% |
Whole percentages, as the Department of Defense tables print them: its instruction says decimals imply more precision than the method has. The equations were fitted to Navy personnel who averaged 21.6% body fat (men) and 27.0% (women), so figures far from those are the least certain.
How it works
The Navy method predicts body fat from a few tape measurements. For men it uses the difference between waist and neck. For women it uses waist plus hips minus neck. Height enters both equations. A larger waist raises the estimate, and a larger neck or greater height lowers it.
James Hodgdon and Marcie Beckett developed the equations at the Naval Health Research Center in San Diego in 1984. They measured 602 Navy men and 214 Navy women with a tape and by underwater weighing, then fitted equations that predict body density from the tape measurements and height. Density is turned into percent fat with Siri’s 1961 equation, the same step the reports use.
The calculator shows two versions of the result. The headline is the 1984 equation as written in the reports. Beside it is the form the Department of Defense printed in its 2002 instruction, which gives percent fat directly from measurements in inches. The Naval Health Research Center produced that form in 1999 by fitting the Navy data again, and wrote that the two give virtually the same results once rounded to the nearest percent. They agree closely but not exactly: across the charts on this page they are never more than 0.7 of a point apart.
The formula
Men, all lengths in cm
density = 1.0324
− 0.19077
× log10(waist − neck)
+ 0.15456 × log10(height)
Women
density = 1.29579
− 0.35004
× log10(waist + hip − neck)
+ 0.22100 × log10(height)
body fat %
= 100 × (4.95 ÷ density − 4.5)
cm = inches × 2.54The 2002 Department of Defense form, with all lengths in inches:
- Men: % body fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: % body fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Worked example
A man who is 5 ft 11 in tall, with a waist of 35.5 in and a neck of 15 in.
- In centimeters: waist 35.5 × 2.54 = 90.17, neck 15 × 2.54 = 38.10, height 71 × 2.54 = 180.34.
- Waist minus neck: 90.17 − 38.10 = 52.07 cm.
- Density: 1.0324 − 0.19077 × log10(52.07) + 0.15456 × log10(180.34) = 1.0324 − 0.3275 + 0.3487 = 1.0536.
- Body fat: 100 × (4.95 ÷ 1.0536 − 4.5) = 19.8%.
- The 2002 form in inches: 86.010 × log10(20.5) − 70.041 × log10(71) + 36.76 = 19.9%.
A woman of 5 ft 5 in with a waist of 29 in, hips of 39 in and a neck of 13 in gets 28.3% from the 1984 equation.
How accurate the Navy method is
- In the 1984 study. Against underwater weighing, the equation for men had a standard error of 3.52 percentage points of body fat and the equation for women 3.72. A standard error of about 3.5 means that for roughly two people in three the estimate fell within 3.5 points of the underwater weighing figure, and for the rest it was further off.
- On other groups. When the equations were checked on people who were not used to build them, the standard error was 2.70 points for 100 Navy men, 4.04 for 80 Navy women and 4.36 for 66 women in the Canadian Forces.
- Against a more detailed model. In 1999 the Naval Health Research Center compared the equations with a four-compartment model of body composition in a newer sample. On average they read 0.8 of a point high for men and 2.0 points high for women, with a standard error of 3.15 points for men and 3.12 for women.
- Against DXA. A 2025 study of 62 people from the military healthcare system compared the Department of Defense circumference method with DXA. The two were moderately correlated: r = 0.62 in the 25 men and 0.73 in the 37 women. In the women the circumference figure was 1.7 points lower on average, with limits of agreement from 14.2 points lower to 10.8 points higher.
- Who was measured. The equations were built on Navy personnel: men aged 18 to 56 and women aged 18 to 44. An equation fitted to one group describes people unlike that group less well. The neck is subtracted in both equations, so a larger neck lowers the estimate whatever the reason for its size.
Is this the test the military uses?
Not as an official result. In 2002 the Department of Defense told all services to measure body fat with this circumference method, using tables built from the Hodgdon and Beckett equations, with each site measured three times and the result rounded to a whole percent.
The rules have changed since. The instruction was updated in 2022, and the Uniformed Services University’s Human Performance Resources page says that as of 1 January 2026 the military uses the waist-to-height ratio to assess body composition. It also says the Army moved to a tape test at a single site under a 2023 directive, and that the Marine Corps has kept a tape test as a secondary assessment.
Plates & Pace is not affiliated with the US Navy or the Department of Defense. For anything official, use your service’s current instruction.
Questions
How does the Navy body fat calculator work?
It puts tape measurements and height into equations fitted to Navy personnel in 1984. For men the equation uses waist minus neck, and for women waist plus hips minus neck. The result is a body density, which is converted to a body fat percentage. A man of 5 ft 11 in with a 35.5 in waist and a 15 in neck comes out at 19.8%.
Where do I measure my waist for the Navy method?
It differs by sex. Men measure around the abdomen at the level of the navel. Women measure the natural waist, the narrowest point of the abdomen, usually about halfway between the navel and the lower end of the breastbone, and also measure the hips over the fullest part of the buttocks, seen from the side. Everyone measures the neck just below the larynx. The measuring guide has the details.
How accurate is the Navy body fat calculator?
In the study that produced it, the standard error was 3.52 points of body fat for men and 3.72 for women against underwater weighing. So a result of 20% is best read as roughly 16 to 23%, and for about one person in three the underwater weighing figure was outside even that. Later comparisons with other methods are in the accuracy section.
Why does another Navy body fat calculator give a slightly different number?
There are two published forms of the equation. The 1984 reports predict body density from measurements in centimeters. The Department of Defense’s 2002 instruction gives percent fat directly from inches, from a later fit to the same Navy data. This page shows both: 19.8% and 19.9% for the example man. Official tables also round each measurement to the half inch and the result to a whole percent.
Does the military still use this tape test?
Rules differ by service and have changed. The Uniformed Services University’s Human Performance Resources page says that as of 1 January 2026 the military uses the waist-to-height ratio to assess body composition, that the Army moved to a tape test at a single site under Army Directive 2023-11, and that the Marine Corps has kept a tape test as a secondary assessment. This calculator applies the 1984 Navy equations and is not an official assessment.
What was the average body fat in the Navy study?
By underwater weighing, the 602 men averaged 21.6% body fat (standard deviation 8.1) and the 214 women 27.0% (standard deviation 6.9). Those are averages of the Navy personnel measured in 1984. They are not targets, and this page does not grade results.
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Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Report No. 84-11. Naval Health Research Center, San Diego; 1984. DTIC accession ADA143890.
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. Report No. 84-29. Naval Health Research Center, San Diego; 1984. DTIC accession ADA146456.
- Hodgdon JA, Friedl K. Development of the DoD body composition estimation equations. Technical Document No. 99-2B. Naval Health Research Center, San Diego; 1999. DTIC accession ADA370158.
- Department of Defense. Instruction 1308.3, DoD Physical Fitness and Body Fat Programs Procedures. 5 November 2002, since replaced. Enclosure 3: body fat assessment procedures, equations and measurement sites. The linked copy is not on a Department of Defense site.
- Human Performance Resources by CHAMP, Uniformed Services University. How the military measures body composition. Updated 27 July 2026.
- Combest TM, Khan J, Tufano JJ, Lane M, Watson NL, Altom KR, Moon JR. Comparison of four body composition methods: circumference measurements, eight-point bioelectrical impedance analysis up to 500 and 1000 kHz to dual-energy X-ray absorptiometry to measure body fat percentage. Military Medicine. 2025;190(3-4):e642-e648.
- National Institute of Standards and Technology. Guide for the Use of the International System of Units (SI), Special Publication 811, Appendix B.9: 1 inch = 2.54 cm and 1 lb = 0.4535924 kg.