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Body Fat Calculator

Estimate body fat percentage with the US Navy method.

Units
Sex
cm
kg
cm
cm
cm

Measure the neck just below the voice box, the waist at the belly button (men) or the narrowest point (women), and the hips at the widest point. Keep the tape level and relaxed.

Estimated body fat

Fat mass
Lean mass
Categories (American Council on Exercise)

Results are estimates for general information only and are not medical advice. Talk to a doctor or other qualified health professional about your health. Read our disclaimer.

When to use it

Use this calculator to estimate your body fat percentage at home with only a tape measure. It uses the US Navy method, which works out body fat from your height and the size of your neck, waist and, for women, hips. It is a useful way to track progress when you are changing your diet or training, because the scale alone cannot tell fat from muscle.

How to use it

  1. Choose your Units: Metric (cm, kg) or US (ft, lb).
  2. Choose your Sex.
  3. Enter your Height and Weight.
  4. Measure and enter your Neck, Waist and, for women, Hips.
  5. Read your Estimated body fat, Fat mass, Lean mass and the category it falls in.

How to measure

Stand up straight and relax. Measure the neck just below the voice box. For men, measure the waist at the belly button. For women, measure the waist at its narrowest point and the hips at the widest point. Keep the tape level and snug, but not tight, and do not pull your stomach in.

Worked example

A woman is 168 cm tall and weighs 68 kg. Her neck is 34 cm, waist 78 cm and hips 98 cm. The estimate is 28.6% body fat, in the Average range of 25–31%. That means about 19.5 kg of fat mass and 48.5 kg of lean mass, which includes muscle, bone, organs and water.

If she measures again in two months and her waist has dropped while her weight stays the same, the result will show lower body fat and more lean mass.

Tips

  • Measure at the same time of day. First thing in the morning, before eating, gives the most consistent results.
  • Take each measurement twice. If the numbers differ, use the average.
  • Use the same tape. A soft, non-stretchy tailor’s tape gives the most reliable readings.
  • Watch the trend, not one number. A steady fall over months matters more than a single reading.

Common mistakes

  • Pulling the tape too tight. This makes the waist smaller and the result too low.
  • Measuring the waist in the wrong place. Men and women use different points. Follow the guide above.
  • Mixing units. If your tape is in inches, switch the units to US first.

This is a general estimate, not a medical test. Talk to a doctor if you have concerns about your weight or health.

Frequently asked questions

How accurate is this method?

The US Navy tape method is usually within about 3 to 4 percentage points of lab methods for most people, but it can be further out for very muscular or very lean bodies. It is best for tracking change over time with the same tape and technique.

Why do women need a hip measurement?

Women tend to store more fat around the hips, so the formula for women uses neck, waist and hips. The formula for men uses neck and waist only.

Is body fat better than BMI?

They measure different things. BMI uses only height and weight, so it cannot tell muscle from fat. A body fat estimate takes body shape into account. Using both, along with waist size, gives a fuller picture.

What is a healthy body fat percentage?

The categories shown come from the American Council on Exercise. For women, 21 to 31% covers the fitness and average ranges, and for men it is 14 to 24%. Healthy ranges also change with age, so ask a doctor what suits you.

How often should I measure?

Every two to four weeks is enough. Body fat changes slowly, and daily measurements mostly show water and tape differences.

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