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Body Fat Calculator: U.S. Navy Tape Method

By Hesaplayıcı

The body fat calculator estimates which part of your weight is fat with the tape measure method of the U.S. Navy. Enter your sex, weight, height, neck and waist circumference; women also enter the hip circumference. The calculator shows the body fat percentage, the fat mass, the lean body mass and your class in the ACE table, step by step.

Just below the larynx, with the tape level.

Men: at the navel. Women: at the narrowest point. Do not pull your stomach in.

Worked example: A man of 80 kg and 178 cm with a 90 cm waist and a 38 cm neck

Body fat

20.10%

Fat mass
16.1 kg
Lean body mass
63.9 kg
Step by step

  1. girth = waist − neck

    girth = 90 − 38 = 52 cm

  2. body density = 1.0324 − 0.19077 × log10(girth) + 0.15456 × log10(height)

    body density = 1.0324 − 0.19077 × log10(52) + 0.15456 × log10(178) = 1.05

  3. Body fat

    body fat = 495 / body density − 450

    body fat = 495 / 1.05286 − 450 = 20.10%

  4. Fat mass

    fat mass = weight × body fat

    fat mass = 80 × 20.1% = 16.1 kg

  5. Lean body mass

    lean mass = weight − fat mass

    lean mass = 80 − 16.1 = 63.9 kg

health.body-fat

How to use

  1. Choose your Units: Metric (kg, cm), Pounds (lb; ft, in) or Stones (st, lb; ft, in). With pounds or stones, the circumferences are in inches.
  2. Choose your Sex: Female or Male.
  3. Enter your Weight and your Height in the units you chose.
  4. Enter your Neck circumference, measured just below the larynx.
  5. Enter your Waist circumference: men measure at the navel, women at the narrowest point.
  6. Women: enter your Hip circumference, measured at the widest point.
  7. Press Calculate.
Neck measurement: the tape goes horizontally around the neck just below the larynx.
Neck: just below the larynx, the tape level and snug, not tight.
Waist measurement for men: the tape goes horizontally around the waist at the level of the navel.
Waist, men: at the level of the navel.
Waist measurement for women: the tape goes horizontally around the narrowest point of the waist.
Waist, women: at the narrowest point, above the navel.
Hip measurement: the tape goes horizontally around the hips at the widest point.
Hip: at the widest point, in the equation for women only.

Formula

  • Men: body density = 1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)
  • Women: body density = 1.29579 − 0.35004 × log10(waist + hip − neck) + 0.221 × log10(height)
  • Body fat (%) = 495 / body density − 450
  • Fat mass = weight × body fat
  • Lean body mass = weight − fat mass

All circumferences and the height are in centimetres; with pounds or stones, the calculator converts inches to centimetres first (1 in = 2.54 cm). log10 is the base-10 logarithm. The density equations are the ones Hodgdon and Beckett published in 1984 for U.S. Navy personnel. The second step is the Siri equation, which turns body density into percent fat. Body fat is rounded to 0.1 and the masses to 0.1 kg, or to 0.1 lb with pounds or stones. The classes are from the ACE table: essential fat, athletes, fitness, average and obese.

Worked example

The worked example on this page shows a man of 80 kg and 178 cm with a 90 cm waist and a 38 cm neck. The steps give the girth, the body density, the body fat percentage, the fat mass and the lean mass.

Limits

The method is an estimate; it does not measure fat directly. The error grows for very muscular people, for older adults and for people who store fat away from the waist. The place and the tension of the tape change the result, so measure at the same place each time. The calculator does not use age or skinfolds. It gives no result for measurements that do not fit together, such as a waist thinner than the neck. For adults only; the result is not medical advice.

Frequently Asked Questions

What is a healthy body fat percentage?

In the ACE table the average range is 18–24% for men and 25–31% for women. The fitness class is 14–17% for men and 21–24% for women. From 25% for men and 32% for women the class is obese.

How accurate is the tape measure method?

It is an estimate. It can differ by about 3–4 points from underwater weighing or a DEXA scan. If you measure at the same place and the same time of day, it is good enough to follow a change.

Why is the hip needed for women only?

The equation for women uses waist + hip − neck, because women store more fat around the hips. The equation for men uses waist − neck only.

Can I measure in inches?

Yes. Choose Pounds or Stones under Units, then enter your height in feet and inches and the circumferences in inches. The calculator converts them to centimetres; the fat mass and lean mass are in pounds.

Is body fat percentage the same as BMI?

No. BMI comes from weight and height only and cannot tell muscle from fat. Body fat percentage estimates which part of your weight is fat.

Calculation rules

  • The method is the U.S. Navy circumference method (Hodgdon and Beckett, 1984). It finds body density first; the Siri equation (495 / density − 450) turns density into percent fat. Measurements are in centimetres and the logarithm is base 10.
  • Men use waist − neck; women use waist + hip − neck. The hip is not used for men.
  • Body fat is rounded to 0.1. Fat mass = weight × the rounded body fat; lean mass = weight − fat mass. Both are rounded to 0.1 kg; with pounds or stones they are in lb, rounded to 0.1 lb.
  • The classes are from the American Council on Exercise (ACE) table. The table is in whole numbers; a class starts at its lower bound, so 13.5% is still “athletes” for a man.
  • The method is an estimate; it can differ by about 3–4 points from underwater weighing or a DEXA scan. For adults only; the result is not medical advice.
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