Free body composition & weight tool
Body Fat Percentage Calculator (U.S. Navy Method) with Chart
The U.S. Navy body fat calculator estimates body fat percentage from height and tape measurements. For men it uses neck and waist; for women it adds hip. A 5 ft 10 in man with a 15.5 in neck and 34 in waist comes out near 16.5% body fat. Enter your measurements below to see your estimate, the ACE category and a BMI-based comparison.
Prepared by Prospyr · Reviewed October 3, 2026 · Free, no sign-up, runs in your browser
Around the neck, tape flat on the skin with even tension.
Abdomen at the level of the navel, relaxed.
An estimate with a wide margin of error, not a diagnosis. Decision support only; it does not replace clinical judgment.
Body fat, U.S. Navy method
16.5%
ACE category: Fitness
Fat mass
29.7 lb
Lean mass
150.3 lb
BMI-based estimate (Deurenberg 1991), for comparison
22.8%
The two methods differ by 6.3 points. Each has a published error of several points, so neither is exact.
Body fat percentage chart (ACE categories)
General categories published by the American Council on Exercise. They describe where an estimate falls; they are not health cutoffs.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and higher | 25% and higher |
U.S. Navy body fat formula, with a worked example
Both equations use inches and base-10 logarithms.
- 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, man: height 70 in, neck 15.5 in, waist 34 in. Waist − neck = 18.5, and log₁₀(18.5) = 1.267, so 86.010 × 1.267 = 108.99. log₁₀(70) = 1.845, so 70.041 × 1.845 = 129.23. Then 108.99 − 129.23 + 36.76 = 16.5% body fat.
Worked example, woman: height 65 in, neck 13 in, waist 29 in, hip 40 in. Waist + hip − neck = 56, log₁₀(56) = 1.748, so 163.205 × 1.748 = 285.3. log₁₀(65) = 1.813, so 97.684 × 1.813 = 177.1. Then 285.3 − 177.1 − 78.387 = 29.8%.
Body fat percentage chart: what the ACE categories mean
The chart under the calculator lists the American Council on Exercise categories for women and men: essential fat, athletes, fitness, average and obese. Women have higher ranges; ACE explains that women need more body fat to maintain menstruation and the ability to have children. The calculator highlights your row, rounding your estimate to the nearest whole percent first, because the printed ranges are whole numbers.
These are descriptive bands from a fitness organization. They are not diagnostic cutoffs and they do not say what percentage is right for any one person.
Navy method vs the BMI-based Deurenberg estimate
The calculator also runs the adult Deurenberg formula, BF% = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex = 1 for men and 0 for women. It came from 1,229 people and reports a standard error of about 4.1 points. The authors also noted that it slightly overestimates body fat in obese subjects.
Showing both is on purpose. When they agree, the estimate is steadier. When they split, check your measurements first, then treat the result as a range, not a point. For BMI on its own, see the BMI calculator; for the lean side of the same split, the lean body mass calculator.
How to take the tape measurements
- Stand relaxed with weight on both feet. Use a flexible tape, snug but not compressing the skin.
- Neck: around the neck with the tape flat on the skin and even tension.
- Waist: men across the navel; women at the narrowest point. Measure after breathing out normally.
- Hip (women): around the fullest part of the buttocks.
- Measure twice and use the average. Repeat at the same spots to compare over weeks.
Practices that offer body contouring or weight management can keep these measurements with each visit in the patient chart so changes are easy to see.
Frequently asked questions
How does the U.S. Navy body fat calculator work?
It estimates body fat from height and circumference measurements using equations published by Hodgdon and Beckett in 1984. Men use neck and waist at the navel; women use neck, narrowest waist and hip. Because it needs only a tape measure, it is easy to repeat, but it is an estimate, not a body scan.
What is the U.S. Navy body fat formula?
With lengths in inches, men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. The result is a percentage of body weight.
What is a good body fat percentage chart to use?
The American Council on Exercise (ACE) publishes common categories. Women: essential fat 10 to 13%, athletes 14 to 20%, fitness 21 to 24%, average 25 to 31%, obese 32% and higher. Men: 2 to 5%, 6 to 13%, 14 to 17%, 18 to 24%, and 25% and higher. The chart above highlights your category.
How accurate is a body fat calculator?
Every calculator is an estimate. The Deurenberg BMI formula reports a standard error of about 4.1 percentage points, and circumference methods depend heavily on where the tape sits. Measure at the same spots, at the same time of day, and compare your own results over time instead of trusting one number.
Why does the BMI-based estimate differ from the Navy estimate?
They use different inputs. The Deurenberg formula (1991) uses BMI, age and sex, so it cannot see where weight is carried. The Navy method uses neck, waist and hip, so it reacts to waist size. The two often differ by several points, which is within each method's published error.
Where exactly do I measure my neck, waist and hip?
For men, measure the abdomen at the level of the navel. For women, measure the waist at its narrowest point and the hip at the widest part of the buttocks. Measure the neck too. Keep the tape flat on the skin with even tension and stand relaxed.
Does this tell me what body fat I should have?
No. It estimates your current percentage and shows where it falls on a published chart. The ACE categories are general descriptions, not health targets, and this tool does not recommend a goal, diet or treatment.
Sources and scope
- Body composition changes during 8 weeks of military training are not accurately captured by circumference-based assessments. Front Physiol, 2023 (PMC10282178)
Peer-reviewed. Prints the Hodgdon and Beckett (1984) circumference equations (lengths converted from cm) and the measurement sites: abdomen at the navel for men; narrowest waist and widest hip for women.
- Circumference-Based Predictions of Body Fat Revisited: Preliminary Results From a US Marine Corps Body Composition Survey. Front Physiol, 2022 (PMC9008774)
Prints the same equations in inches and cites Hodgdon and Beckett (1984).
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr, 1991 (PubMed 2043597)
Adult formula BF% = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4; SEE 4.1%; slight overestimate in obese subjects.
- American Council on Exercise (ACE). General Body-fat Percentage Categories (table from ACE, archived copy of the ACE blog post)
Essential fat, athletes, fitness, average and obese ranges for women and men used in the chart. The live ACE page no longer carries the table.
An estimate from published equations, not a measurement of body composition and not a diagnosis. Decision support only; it does not replace clinical judgment. It does not recommend a goal, diet or treatment.