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Body Fat Calculator – Body Fat Percentage with a Tape Measure

Estimate your body fat percentage from your height and a few tape-measure readings using the US Navy method. See your body-fat category, how much of your weight is fat and how much is lean mass. No special scales needed.

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How to use the body fat calculator

  1. Choose metric or US units and select your sex.
  2. Enter your height and weight.
  3. Measure and enter your neck and waist. Women also enter their hips.

You’ll see your estimated body fat percentage, your category from the American Council on Exercise, and your fat mass and lean mass.

The US Navy formula

The US Navy developed this method in the 1980s (Hodgdon and Beckett) to estimate body fat quickly with only a tape measure. With measurements in centimetres:

Men: % fat = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: % fat = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450

Worked examples

  • A man who is 175 cm tall with a 38 cm neck and 86 cm waist: body fat ≈ 17.7% — in the “fitness” range. At 75 kg, that is about 13.3 kg of fat and 61.7 kg of lean mass.
  • A woman who is 165 cm tall with a 33 cm neck, 76 cm waist and 100 cm hips: body fat ≈ 29.9% — in the “average” range.

Body fat categories

CategoryMenWomen
Essential fat2–5%10–13%
Athletes6–13%14–20%
Fitness14–17%21–24%
Average18–24%25–31%
Obese25% and over32% and over

Women naturally carry more essential fat than men, which is why the ranges differ.

Other ways to measure body fat

  • DEXA scan — very accurate, but costs money and needs a clinic.
  • Bioelectrical impedance scales — convenient, but readings change with hydration.
  • Skinfold callipers — accurate with a trained tester.
  • Hydrostatic (underwater) weighing — a lab method.

Whichever you use, stick to one method and look at the trend over time rather than a single number.

Getting reliable measurements

Small measuring errors make a big difference: one centimetre on the waist can move the result by about one percentage point. Stand up straight and relaxed, breathe out normally and don’t pull in your stomach. Keep the tape level all the way round, and ask someone to help with the neck measurement if you can. Measuring at the same time of day each time makes your trend much more trustworthy than any single reading.

Next steps

Waist size on its own is also a useful health marker: many health bodies suggest keeping it below half your height. Compare with your BMI, find a healthy weight range with the ideal weight calculator, or use your lean mass in the Katch-McArdle option of the BMR calculator. This is an estimate, not medical advice — see our disclaimer.

Frequently asked questions

How do I measure for the body fat calculator?

Use a soft tape measure on bare skin, snug but not tight. Neck: just below the Adam’s apple, sloping slightly down at the front. Waist: men at the navel, women at the narrowest point. Hips (women): at the widest point of the buttocks. Measure twice and use the average.

How accurate is the US Navy method?

Studies comparing it with lab methods such as DEXA usually find it within about 3 to 4 percentage points for most people. It is less accurate for very muscular people and people with an unusual fat distribution.

What is a healthy body fat percentage?

The American Council on Exercise lists 14–24% as fit to average for men and 21–31% for women. Essential fat — the minimum needed for health — is about 2–5% for men and 10–13% for women.

Why does the calculator need my weight?

Only to show fat mass and lean mass in kg or pounds. The percentage itself comes from your height and circumferences.

Is body fat percentage better than BMI?

It tells you more about body composition. BMI can’t tell muscle from fat, so a muscular athlete may have a high BMI with low body fat. Using both, plus your waist size, gives a fuller picture.

How often should I measure?

Every two to four weeks is enough to see a trend. Measure at the same time of day, ideally in the morning before eating.

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