Free Body Fat Percentage Calculator
Get a Body Fat Estimate From Simple Measurements.
Enter your height and tape measurements to calculate an estimated body fat percentage. See the method, understand its limits, and use consistent measurements for comparison.
Tape-measure estimate. Female and male equations. No account required.
Estimated body fat
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Estimated fat mass
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Estimated fat-free mass
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An equation-based estimate, shown with its method and limitations.
Body Fat Percentage Calculator
An estimate from the U.S. Navy circumference equations — not a direct measurement or a medical assessment.
Your measurements are processed in this page and are not saved by this calculator.
Body Weight Does Not Explain Body Composition.
A tape-based equation offers one way to estimate body fat, but its usefulness depends on consistent measurements and an understanding of its limitations.
Understand the Estimate Behind the Number.
01
Calculate a circumference-based estimate
Height plus neck and waist or abdomen (and hips for the female equation) — no calipers or scans.
02
See the measurements and equation used
Your entries, units and the exact equation are shown with every result.
03
Download results with their limitations
Save or print the estimate together with its method, sources and caveats.
Your Estimate in Three Steps.
1
Select the applicable equation and units.
Choose the female or male equation, and inches/pounds or centimeters/kilograms.
2
Measure the required sites using the instructions.
Each field explains where the tape goes, how to stand and when to breathe out.
3
Review the estimate and its limitations.
Read the result with its method and caveats, then download or print it.
How This Body Fat Percentage Calculator Works
What the sources establish
The equations. This calculator uses the circumference equations commonly called the “U.S. Navy method,” in the percent-fat form published by Hodgdon and Friedl (1999). With every measurement in inches and base-10 logarithms:
- Male: 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76
- Female: 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Where they came from. Hodgdon and Beckett (1984) developed the original equations at the Naval Health Research Center from 602 Navy men aged 18–56 and 214 Navy women aged 18–44, using underwater weighing as the reference. Those originals predicted body density from centimeter measurements; the 1999 report refit the same data to predict percent fat directly in inches and describes the results as virtually the same.
Why female and male inputs differ. This method uses different equations and measurements for female and male reference populations. The male equation uses the abdomen at the navel; the female equation uses the natural waist (the narrowest point of the abdomen) plus the hips. They are different measurements and are never swapped.
Reported fit. In the development samples the 1999 report lists a standard error of estimate of 3.52 percentage points for men and 3.61 for women. That describes the group studied, not the error for any individual result, so no personal ± range is shown.
Not a current military test. These historical equations are not a current official military body-composition assessment, and this calculator does not follow any service’s official measuring, rounding or eligibility procedures.
This calculator’s own choices
- Units. Centimeters are converted to inches (in = cm ÷ 2.54) before the inch-based constants are applied, and body weight uses kg = lb ÷ 2.2046226218. Applying inch constants to centimeter values would give a wrong answer.
- No rounding of measurements. Your entries are used as typed (up to two decimals). Only the result is rounded, to a whole percentage point.
- Impossible results are withheld. If the equation returns zero or less, or 100% or more, no number is shown — it is never adjusted into a plausible range.
- Neutral caution. Positive estimates below 6% or above 50% show a note that the estimate may be unreliable. These cutoffs are our screening choice, not values from the sources.
- Mass estimates. With your weight: fat mass = weight × body fat % ÷ 100, and fat-free mass = weight − fat mass. Fat-free mass includes muscle, water, bone, organs, and other nonfat tissue. It is not the same as muscle mass.
Circumference equations can differ substantially from an individual’s actual body composition. A precise-looking number does not establish accuracy.
Use the same method and landmarks each time. Small changes may reflect measurement variation rather than a real body-composition change.
Sources
- Development of the DoD Body Composition Estimation Equations (Technical Document 99-2B) (opens in a new tab)
J. A. Hodgdon & K. Friedl · Naval Health Research Center · September 1999
The percent-fat equations and constants used here, in inches with base-10 logarithms (men n = 594, R = 0.903, SEE 3.52% fat; women n = 202, R = 0.856, SEE 3.61% fat).
- Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height (Report 84-11) (opens in a new tab)
J. A. Hodgdon & M. B. Beckett · Naval Health Research Center · March 1984
The original male equation, developed on 602 Navy men aged 18–56 against underwater weighing; neck and abdomen (navel) landmarks and measuring technique.
- Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height (Report 84-29) (opens in a new tab)
J. A. Hodgdon & M. B. Beckett · Naval Health Research Center · June 1984
The original female equation, developed on 214 Navy women aged 18–44 against underwater weighing; neck and minimal-abdominal-width landmarks; a note that such equations tend to be population specific.
- Guide 4: The Body Composition Assessment (BCA) (opens in a new tab)
U.S. Navy Physical Readiness Program (OPNAVINST 6110.1 series) · January 2016
Step-by-step tape placement for neck, abdomen, natural waist and hips (greatest protrusion of the buttocks), posture, breathing and repeat measurements. Its half-inch rounding and table lookup are official procedures this calculator does not implement.
Who This Calculator Is For
A good fit
Adults who want an educational, circumference-based body fat estimate and a consistent way to measure.
May be unsuitable or less reliable for
- Pregnancy and the postpartum period.
- Very muscular physiques.
- Body proportions unlike the reference population.
- Conditions affecting fluid balance or body shape.
- Situations requiring clinical body-composition assessment.
This calculator does not diagnose or identify any of these circumstances.
Body Fat Percentage Calculator FAQ
How is body fat percentage estimated?
- This calculator uses equations that predict body fat from height and body circumferences. They were developed by comparing tape measurements with underwater weighing in U.S. Navy personnel. The result is an estimate, not a direct measurement.
Why do female and male equations differ?
- This method uses different equations and measurements for female and male reference populations. Each equation was developed on its own reference group with its own measurement sites, so the constants and inputs are different.
Where do I place the tape?
- Neck: just below the larynx (Adam’s apple). Male equation: around the abdomen at the navel. Female equation: around the natural waist — the narrowest point of the abdomen — and around the hips at the greatest protrusion of the buttocks. Keep the tape level and snug without compressing the skin, and measure the abdomen or waist at the end of a normal breath out.
Is waist the same measurement for both equations?
- No. The male equation uses the abdomen at the level of the navel. The female equation uses the natural waist, usually about halfway between the navel and the lower end of the breastbone. The calculator keeps them as separate fields.
How accurate is this calculator?
- Circumference equations can differ substantially from an individual’s actual body composition. A precise-looking number does not establish accuracy. In the original development samples, the reported standard error of estimate was about 3.5–3.6 percentage points, which describes those groups rather than any one person. Measurement technique also affects the result.
Is this the current official Navy body-fat test?
- These historical equations are not a current official military body-composition assessment, and this calculator does not follow any service’s official measuring, rounding or eligibility procedures.
Can bodybuilders use the estimate?
- They can, but circumference equations may be less reliable for very muscular physiques, because larger muscle around the neck, waist or hips changes the measurements in ways the equations were not developed for. Use the result with that caution.
Is fat-free mass the same as muscle mass?
- No. Fat-free mass includes muscle, water, bone, organs, and other nonfat tissue. It is not the same as muscle mass.
Why did the calculator reject my result?
- If the equation returns zero or less, or 100% or more, that is not a possible body fat percentage, so no number is shown. This usually means a unit mix-up, a measurement at the wrong landmark, or a typing error — or the equation may simply not fit your measurements.
Can I use the result to prove fat loss?
- No. A change between two estimates can reflect measurement variation as well as real change. Use the same method and landmarks each time. Small changes may reflect measurement variation rather than a real body-composition change.
Is my information saved?
- No. Your measurements are processed in this page and are not saved by this calculator. Nothing is sent to a server or stored in your browser.
Measure Consistently. Understand the Estimate.
Enter your tape measurements and review your result with the method and limitations clearly explained.