Estimate adult body fat percentage from tape measurements using the U.S. Navy circumference method. Works for men and women in US or metric units. Results stay in your browser.
Estimated body fat from circumference equations — not a direct measurement, DEXA scan, or official Navy BCA pass/fail. ACE categories are fitness reference bands, not diagnoses.
A body fat calculator estimates body fat percentage from body measurements. The tool on this page uses the U.S. Navy circumference method (Hodgdon and Beckett, 1984): height plus waist and neck for men, and height plus waist, neck, and hip for women.
Weight is not part of the Navy percentage equation. If you enter weight, the page also shows estimated fat mass (weight × body fat %) and lean body mass (weight − fat mass) derived from that estimate.
Men and women use different equations and different ACE category bands. Results are estimates. Tape placement, clothing, and posture move the number. This is not a DEXA scan, caliper test, or official Navy Body Composition Assessment pass/fail.
Enter sex, height, and tape measurements above. You get an estimated body fat percentage from the Navy equations — not a measured body-fat reading.
Choose male or female. The Navy equations are different, and women also need a hip measurement.
Use pounds with feet and inches, or kilograms with centimeters. Switching units converts values already entered.
Measure neck just below the larynx. Men measure waist at the navel; women measure the natural waist and hips at the widest point. Weight is optional for fat and lean mass.
The result updates as you type: estimated body fat %, ACE category, fat mass, and lean mass. Open the formula breakdown if you want the substitution.
Input
5 ft 10 in
180 lb
Neck 15 in
Waist 34 inOutput
Estimated body fat 17.5% — ACE Fitness (14–17%)
Fat mass 31.5 lb · lean mass 148.5 lbHeight = 70 in. Circumference term = 34 − 15 = 19. 86.010 × log10(19) − 70.041 × log10(70) + 36.76 ≈ 17.51, shown as 17.5%. Weight is used only for 180 × 0.175 = 31.5 lb fat.
Input
5 ft 4 in
140 lb
Neck 13 in
Waist 29 in
Hip 39 inOutput
Estimated body fat 29.2% — ACE Average (25–31%)
Fat mass 40.9 lb · lean mass 99.1 lbHeight = 64 in. Circumference term = 29 + 39 − 13 = 55. 163.205 × log10(55) − 97.684 × log10(64) − 78.387 ≈ 29.21, shown as 29.2%.
Input
177.8 cm · 81.6 kg · neck 38.1 cm · waist 86.4 cmOutput
Estimated body fat 17.5% — same as the US exampleMeasurements convert to inches, then the same Navy log equations run. Equivalent inputs produce the same percentage.
This tool implements the Hodgdon and Beckett (1984) U.S. Navy circumference equations in inches. Metric entries are converted to inches before the logarithms run. That inch form is the result you see.
A centimeter body-density form (495 / D − 450) is the same Hodgdon–Beckett relationship written differently. It can differ by about 0.1 percentage point after rounding. We do not mix the two forms.
The Navy percentage does not use body weight. Fat mass and lean mass are derived afterward if weight is present. Categories follow the American Council on Exercise (ACE) adult chart and are fitness reference bands, not diagnoses.
This is not the official 2026 Navy Body Composition Assessment table or waist-to-height pass/fail rule.
Formula
Men (inches): %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women (inches): %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Fat mass = body weight × (%BF ÷ 100)
Lean mass = body weight − fat massFitness reference bands shown on this page. They are not medical diagnoses.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Source: American Council on Exercise body composition chart, as commonly published. Essential fat is a physiological minimum, not a goal.
Different tools answer different questions. None of these is universally “best.”
| Method | What you enter | What you get |
|---|---|---|
| Navy tape (this page) | Height, waist, neck (+ hip for women) | Estimated body fat % |
| BMI calculator | Height and weight | Weight-for-height screen |
| DEXA | Clinic scan | Tissue-specific estimate |
| BIA scale | Stand-on device | Impedance-based estimate |
| Skinfold calipers | Pinch sites | Estimate from subcutaneous fat |
Cost, access, and error sources differ. Use one method consistently if you are tracking change.
This page owns estimated body fat percentage. Use a different tool when the question is BMI, formula weight, calories, or lean mass planning.
| Related tool | Use this tool when | Use related tool when |
|---|---|---|
| BMI Calculator | You want a tape-measure body-fat estimate. | You only have height and weight and want a BMI screening number. |
| Lean Body Mass Calculator | You want lean mass derived from this Navy estimate. | You already have a body-fat % and want dedicated LBM formulas. |
| Calorie Calculator | You only need a composition estimate. | You need BMR, TDEE, or a daily calorie target. |
| Ideal Weight Calculator | You want fat and lean mass from measurements you have now. | You want Devine, Robinson, Miller, or Hamwi height-based ranges. |
Men: navel, after a normal exhale. Women: natural waist (narrowest point). Measuring over a belt or sucking in changes the log term.
Place the tape just below the larynx, level, without tensing the neck.
The female Navy equation requires waist + hip − neck. Without hips there is no valid female result.
Stay in one unit system. Use the US / Metric toggle so values convert instead of mixing systems.
The male formula uses log10(waist − neck). If waist is not larger than neck, the logarithm is undefined and the calculator shows an error instead of NaN.
This is an estimate from circumferences. DEXA, hydrostatic weighing, BIA, and calipers will not match it exactly.
Track one method under the same conditions. Method-to-method gaps are expected.
Use a soft tape, same tightness, same time of day if you are logging trends.
Use DEXA or another clinical method. This page is a field estimate.
The Navy percentage needs tape measurements. Use the BMI calculator for a height–weight screen.
Current Navy body-composition rules are not this civilian Hodgdon–Beckett calculator.
Use the lean body mass calculator.
Step-by-step chains that connect related tools for common tasks.
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A body fat calculator estimates the percentage of body weight that is fat. This one uses the U.S. Navy circumference method from height and tape measurements. It does not measure fat tissue directly.
It applies Hodgdon and Beckett’s 1984 log10 equations. Men use waist minus neck and height. Women use waist plus hip minus neck and height. All inputs are converted to inches first.
Select sex, choose US or metric units, then enter height, neck, and waist. Women also enter hips. The estimated body fat percentage appears as you type.
Everyone needs height, neck, and waist. Women also need hip circumference. Weight is optional and is used only for fat mass and lean mass.
Neck: just below the larynx. Male waist: at the navel after a normal exhale. Female waist: the narrowest point of the natural waist. Hips: the widest point of the buttocks. Use a level, snug tape on bare skin or thin clothing.
ACE lists average adult bands as 18–24% for men and 25–31% for women, with lower “fitness” and “athletes” bands. Those are fitness reference ranges, not personalized medical targets.
Yes. The Navy equations differ, women require a hip measurement, and ACE category bands are higher for women because essential fat is higher.
It is a population-derived estimate. It can differ from DEXA, hydrostatic weighing, and BIA. Tape error of one inch at the waist can move the result by a few percentage points. Use it for consistent tracking, not as a lab measurement.
Yes. US units are the default. Metric values are converted to inches before the Navy equations run, so equivalent inputs produce the same percentage.
BMI uses only height and weight. Body-fat estimation here uses additional circumferences. Neither is a direct composition measurement. Compare the two on the BMI calculator if you want the height–weight screen.
No. It is a tape-measure method. That is why people search for a body fat calculator without calipers.
BIA scales estimate from electrical impedance and hydration. The Navy method estimates from circumferences. Different inputs, different models, different numbers.
Yes, if you repeat the same landmarks, tape tension, and time of day. Month-to-month trends with one method are more useful than comparing this number to a scale or a gym scan.
Yes. No signup. The calculation runs in your browser. Measurements are not uploaded for the calculation. A share link is created only if you choose to share. Optional history stays on this device.
Body fat is calculated in your browser. Measurements are not uploaded to EverydayTools for the core calculation. Optional local save uses this device only. Sharing a link includes only the values you choose to put in that URL.
Navy percentages use the inch log10 equations to one decimal. Metric inputs are converted to inches first. Equivalent US and metric entries match. The centimeter density form can differ by about 0.1 after rounding and is not used for the displayed result.
Core math is client-side JavaScript. No server request is required to estimate body fat.
Recalculate the male example (70 in, waist 34, neck 15) by hand: 86.010 × log10(19) − 70.041 × log10(70) + 36.76 ≈ 17.5%.
Limitations: Estimate only. Not DEXA, not official Navy BCA, not a diagnosis. Technique and method choice change the number.
General body-fat estimate only — not medical advice, diagnosis, or treatment. Consult a healthcare provider for personal health decisions.
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Reviewed by EverydayTools Editorial Team on 2026-09-20.
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