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Estimate body fat % with the U.S. Navy tape-measure method, plus fat vs. lean mass. Free, no signup.

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Body Fat Percentage Calculator — Find Your Real Body Composition

Your weight alone does not tell you how much of you is fat and how much is muscle. With a tape measure and the U.S. Navy circumference method, get your body fat percentage, your ACE fitness category, and your fat mass versus lean mass in seconds.

The Navy formulas differ by sex: women also need a hip measurement, because female fat distribution differs from male fat distribution.

Example: 5 ft 10 in = 70 inches.

Measure just below the Adam’s apple, tape snug but not tight.

Measure at the widest point around the hips and buttocks.

Men: measure at the navel. Women: measure at the narrowest point of the waist.

Needed only for the fat mass and lean mass split — it does not change the percentage.

Body fat percentage
0%
U.S. Navy circumference method
ACE category
—
—
Fat mass
0
pounds of body fat
Lean mass
0
pounds of muscle, bone, and water
EssentialAthleteFitnessAverageObese
How to read this:
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All math happens in your browser. Your measurements and weight are never uploaded or stored anywhere.

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No account, no email, no app. Open the page and calculate as many times as you like.

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Unlimited body fat estimates with category and mass breakdown — free, no limits.

How to use the body fat percentage calculator

  1. 1Pick your units and sex

    Use inches and pounds or centimeters and kilograms, then choose male or female — the Navy formula is different for each.

  2. 2Measure with a flexible tape

    Neck below the Adam’s apple, waist at the navel (men) or narrowest point (women), and hips at the widest point (women). Keep the tape level and snug, not tight.

  3. 3Enter height and weight

    Height feeds the Navy formula; weight is used only to split your total into fat mass and lean mass.

  4. 4Read your result

    See your body fat percentage, your ACE category, and how many pounds or kilograms are fat versus lean tissue.

Why people use the Navy method

No lab, no calipers

The U.S. Navy method needs only a cloth tape measure — no DEXA scan, no underwater weighing, no skinfold calipers, and no appointment.

Validated against lab methods

Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 and validated against hydrostatic weighing, with a typical margin of about 3 to 4 percentage points.

Beats BMI for athletes

BMI cannot tell muscle from fat, so muscular people look “overweight” on BMI. Circumference measurements track where fat actually sits.

Fat mass and lean mass split

Your percentage alone does not show progress if your weight changes. Fat mass and lean mass show whether you are losing fat, gaining muscle, or both.

ACE categories, explained

Your result is placed on the American Council on Exercise scale — essential, athlete, fitness, average, or obese — with the range for your sex shown alongside.

Imperial and metric

Enter inches and pounds or centimeters and kilograms. Metric values are converted to inches before the formula runs, so the result is identical either way.

Body fat percentage calculator FAQs

What is the U.S. Navy body fat formula?
For men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women: body fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. All measurements are in inches (metric inputs are divided by 2.54 first). It was developed in 1984 by Hodgdon and Beckett at the Naval Health Research Center.
How accurate is the Navy method?
Reasonably accurate for a tape-measure method — validation studies put the typical error around 3 to 4 percentage points versus hydrostatic (underwater) weighing. It is best used for tracking changes over time with consistent measuring technique, rather than as a single exact number.
What is a healthy body fat percentage?
On the ACE scale, the fitness range is 14% to 17% for men and 21% to 24% for women, and the average range is 18% to 24% for men and 25% to 31% for women. Essential fat — the minimum for basic health — is 2% to 5% for men and 10% to 13% for women.
Where exactly do I measure my waist?
Men measure at the navel, with the tape level around the body. Women measure at the narrowest point of the waist, usually just above the navel. In both cases, relax, breathe out normally, and do not pull the tape tight or suck in.
Why does the women’s formula need a hip measurement?
Because women naturally store a larger share of body fat around the hips and thighs. Adding hip circumference lets the formula account for that distribution pattern, which the waist and neck alone would miss.
Does my weight change the body fat percentage?
No. The Navy percentage comes only from circumferences and height. Weight is used here only to convert that percentage into fat mass and lean mass — for example, 20% body fat at 200 pounds means 40 pounds of fat and 160 pounds of lean mass.
Why is my result different from a scale or a BMI calculator?
Smart scales use bioelectrical impedance, which swings with hydration, recent meals, and skin moisture. BMI uses only height and weight and cannot distinguish muscle from fat. The Navy method measures your actual body shape, which is why it often disagrees with both — and is usually the more useful of the three for tracking composition.
How often should I re-measure?
Every 2 to 4 weeks is plenty. Body composition changes slowly, and daily tape readings mostly capture water and measurement noise. Measure at the same time of day, with the same tape position, for comparable results.

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