Calculate-Compare-Decide
Estimate your body fat with the official U.S. Navy circumference formula, then check the 2026 two-step BCA — waist-to-height ratio first, body fat percentage second. Live results, no signup.
Measure the neck below the larynx and waist at the navel on a relaxed exhale. How to measure →
| Measure | Value |
|---|
A Navy body fat calculator estimates your body fat percentage from simple tape measurements using the U.S. Navy circumference formula. Men enter height, neck and waist; women also add the hip. It returns an estimated body fat percent and, using the current 2026 Body Composition Assessment, shows whether you'd be within Navy standards.
The Navy uses a log-based circumference formula. Men: %BF = 86.010·log₁₀(waist−neck) − 70.041·log₁₀(height) + 36.76. Women: %BF = 163.205·log₁₀(waist+hip−neck) − 97.684·log₁₀(height) − 78.387. All measurements are in inches; metric inputs are converted automatically.
Use a non-stretch (fiberglass) tape against the skin, kept level and parallel to the floor. Take each reading at the end of a relaxed exhale, measure twice, and average — a third time if they differ by more than an inch.
Just below the larynx; tape slopes slightly down at the front.
Men at the navel; women at the narrowest point. Relaxed exhale.
Widest point over the buttocks, tape level all around.
No shoes, standing tall, heels together, eyes forward.
The Navy method is the core estimate; BMI, lean mass, calories and target weight are derived for context.
Worked example (male, imperial). Height 70 in, neck 15 in, waist 34 in → waist − neck = 19. %BF = 86.010·log₁₀(19) − 70.041·log₁₀(70) + 36.76 = 17.5%.
Worked example (female, imperial). Height 65 in, neck 13 in, waist 30 in, hip 40 in → waist + hip − neck = 57. %BF = 163.205·log₁₀(57) − 97.684·log₁₀(65) − 78.387 = 31.1%.
Metric. Enter centimeters and the tool converts to inches first (÷ 2.54), then applies the same formula — the result is identical either way.
BMI = weight(kg) ÷ height(m)². Fat mass = weight × %BF. Lean body mass = weight − fat mass. Waist-to-height ratio = waist ÷ height (the Navy's Step-1 screen; ≤ 0.55 passes).
Maintenance calories use the Mifflin-St Jeor equation for resting metabolism, multiplied by an activity factor. To reach a target body fat, the tool holds lean mass constant: target weight = lean mass ÷ (1 − target%/100), and fat to lose = current weight − target weight. These are planning estimates, not guarantees.
Set a goal to see the weight and fat change it implies, then log results to watch the trend. Estimates only — real change depends on training, nutrition and individual factors.
Enter a target to see the estimated fat to lose and goal weight, assuming lean mass stays constant.
Press “Log result” on the calculator to save a snapshot. Entries stay in your browser only.
No entries yet — calculate, then press Log result.
The 2026 BCA uses a flat maximum of 26% (men) and 36% (women), applied after the waist-to-height screen. The age-graduated figures below are the older standard, kept for reference. Always verify against current official guidance.
| Sex | Step 1 (WHtR) | Step 2 (max BF) |
|---|---|---|
| Male | ≤ 0.55 | 26% |
| Female | ≤ 0.55 | 36% |
| Age | Male | Female |
|---|---|---|
| 18–21 | 22% | 33% |
| 22–29 | 23% | 34% |
| 30–39 | 24% | 35% |
| 40+ | 26% | 36% |
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
| BMI | Classification |
|---|---|
| < 18.5 | Underweight |
| 18.5–24.9 | Healthy |
| 25.0–29.9 | Overweight |
| 30.0+ | Obese |
| Convert | Factor |
|---|---|
| 1 inch → cm | 2.54 |
| 1 cm → inch | 0.3937 |
| 1 lb → kg | 0.4536 |
| 1 kg → lb | 2.2046 |
All use the Navy formula. Your own numbers will vary — these show how neck, waist, hip and height interact.
waist−neck = 18 → 15.6% body fat. Comfortably within standards.
W+H−N = 55 → 29.5%. Within the 36% cap.
Lower waist relative to neck → 12.9%. Athletic range.
waist−neck = 24 → 25.6%. Over 26%? No — just under; watch the trend.
→ 23.8%. Within standards; WHtR = 0.56 just over Step 1.
Converted to inches → ≈ 28.9% body fat.
A 6-inch waist drop moves body fat from 27.9% to 19.6%.
waist−neck = 19 → 16.8%. Clears both BCA steps.
"Navy body fat" refers to a body fat percentage estimated with the U.S. Navy's circumference method — a formula that turns a few tape measurements into an estimate of how much of your body is fat versus lean tissue. It became popular because it needs nothing more than a tape measure, yet tracks lab methods closely enough to be useful for fitness screening. The rest of your weight, the part that isn't fat, is your lean body mass: muscle, bone, organs and water.
The formula comes from research by Hodgdon and Beckett at the Naval Health Research Center in the 1980s, who related simple circumference measurements to body density and body fat. The equations were adopted across the Department of Defense as an affordable, repeatable way to assess body composition at scale. Decades later they remain the backbone of the Navy's body fat estimate, even as the surrounding standards have been modernized.
The method exploits a simple idea: fat tends to accumulate at the waist (and hips, in women), while the neck stays relatively lean. The difference between those circumferences, scaled against height, correlates with overall body fat. That's why the male formula subtracts neck from waist, and the female formula adds the hip before subtracting the neck — it captures where fat is stored. The logarithms compress the relationship into a form that matches measured body density well.
Circumferences work because body-fat distribution is patterned and predictable enough to model. A larger waist relative to your frame signals more stored fat; a proportionally larger neck signals more lean mass. The method isn't perfect for everyone — very muscular people can read a little high and very lean people a little low — but for the majority it lands within a few points of a DXA scan, which is remarkable for a tape measure.
Accuracy depends on technique. Use a non-stretch tape against the skin, keep it level and parallel to the floor, and take readings at the end of a normal exhale without sucking in or bracing. Measure the neck just below the larynx, the waist at the navel (men) or narrowest point (women), and the hips at their widest. Take each measurement at least twice and average them; if two readings differ by more than an inch, take a third. Small, consistent technique matters more than any single "perfect" number.
Men use height, neck and waist because male fat storage is dominated by the abdomen. Women add the hip because female fat distribution includes the hips and thighs, so the extra circumference improves the estimate. This is also why the female equation uses different constants — it was fitted to female body composition data. Selecting the correct sex in the calculator applies the right equation automatically.
In 2026 the Navy replaced its old height/weight table with a two-step Body Composition Assessment. Step 1 is waist-to-height ratio: divide your waist by your height, and if the result is at or below roughly 0.55 you're within standards and no further measurement is needed. Step 2 applies only if you exceed Step 1 — the Navy then estimates body fat with the circumference formula, and you pass if you're at or below 26% (men) or 36% (women). Meeting either step keeps you within standards, which is why this calculator shows both.
BMI compares weight to height and can't tell muscle from fat, so it mislabels many fit, muscular people as overweight. The Navy circumference method exists precisely to look past that — it estimates actual body composition rather than just mass. Use BMI as a quick screen, but trust the circumference estimate for a more meaningful read on body fat.
The most reliable way to lower a Navy body fat estimate is to reduce waist circumference through fat loss while preserving lean mass. That means a modest, sustained calorie deficit, enough protein to protect muscle (broadly around 0.7–1 gram per pound of body weight for active people), and a mix of strength training and conditioning. Strength work maintains the lean mass that keeps your metabolism up; cardio adds to your energy deficit; sleep and recovery let the changes stick. Crash diets and dehydration tricks don't beat the tape reliably and can hurt your performance on the physical readiness test.
The usual errors are holding the tape at an angle, measuring over clothing, pulling too tight or too loose, sucking in the stomach, measuring at the wrong spot, and taking a single reading. Each can shift the result by a percentage point or more, which matters near a cutoff. Standardize your routine — same time of day, same technique, averaged readings — so your numbers are comparable over time.
The 2026 update shows how quickly military policy can evolve: the height/weight table is gone, waist-to-height leads the assessment, and the body fat cap is now flat rather than age-graduated. Treat this page as an explainer and estimator, and confirm the current requirements against official Navy publications and your Command Fitness Leader before making decisions that affect your record.
A Navy body fat calculator estimates your body fat percentage from simple tape measurements using the U.S. Navy circumference formula. Men enter height, neck and waist; women also add the hip. It returns an estimated body fat percent and, using the 2026 Body Composition Assessment, shows whether you would be within Navy standards.
For men, %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women, %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. Measurements are in inches; this calculator converts metric inputs automatically before applying the formula.
Under the 2026 update (OPNAVINST 6110.1L, Guide-4), the Navy uses a two-step assessment. Step 1 is waist-to-height ratio: passing at or below about 0.55. Step 2, used only if Step 1 is exceeded, allows a maximum body fat of 26% for men and 36% for women. Meeting either step means you are within standards.
The Navy removed the old height/weight table and age-graduated body fat limits. The current method leads with a sex-neutral waist-to-height ratio screen (about 0.55), and only if you exceed it does the Navy estimate body fat, with a single flat cap of 26% for men and 36% for women rather than limits that rise with age.
It is a reliable estimate, not a lab measurement. The Navy circumference method is designed to be consistent and low-cost, and typically lands within a few percent of methods like DXA for most people. It can be less accurate for very muscular or very lean individuals. Use it to estimate and track progress, and rely on an official measurement for records.
Measure the neck just below the larynx (Adam's apple) with the tape sloping slightly down at the front. Measure the waist at the navel for men, and women measure at the narrowest point; take it at the end of a normal exhale with a non-stretch tape parallel to the floor. Round to the nearest half inch and average repeated readings.
Yes. The female Navy formula uses waist plus hip minus neck, so a hip measurement is required. Measure the hips at the widest point over the buttocks, standing with feet together and the tape level and parallel to the floor. Men do not use a hip measurement in the Navy formula.
Waist-to-height ratio is your waist circumference divided by your height in the same units. The Navy adopted it as the first screen because it reflects fat distribution and health risk better than weight alone. A ratio at or below about 0.55 passes Step 1, and no body fat calculation is needed unless you exceed it.
Sailors who exceed the standard are enrolled in a fitness and nutrition improvement program and must still take the physical readiness test with medical clearance. Being over standard can affect eligibility for promotion, schools, and reenlistment, so most sailors work to reduce waist circumference through consistent diet and training.
No. The Navy method uses height plus neck and waist for men, and neck, waist and hip for women, in a log-based formula. The Army's current method uses only the abdomen and body weight. The two produce similar but not identical estimates, and each service applies its own standards.
Age does not change the Navy body fat formula itself. Under the 2026 standard the pass/fail cap is also flat (26% men, 36% women) rather than age-graduated. Age is used here only to estimate maintenance calories via the Mifflin-St Jeor equation in the advanced view.
Yes. Switch the units toggle to centimeters and kilograms and your existing values convert automatically. Internally the tool converts lengths to inches before applying the Navy formula, so metric and imperial produce the same body fat estimate.
About once a month is enough to see a real trend without over-reacting to daily fluctuations from food, water and sodium. Use the progress tracker to log results and focus on the direction over several readings rather than any single measurement.
No. It uses the same published Navy formula and current standards, so results should closely match, but official body composition is measured by trained Command Fitness Leaders and recorded in the Navy's system. Treat this as an accurate estimate for planning and preparation.
No account or upload is needed. Anything you log in the progress tracker is stored only in your own browser on this device, and you can clear it any time with the button in that section.