Body Fat Calculator

Calculate body fat percentage, lean body mass, body composition, and healthy body fat ranges.

Body Fat Calculator

Estimate your body fat percentage from simple tape measurements using the US Navy circumference method. The result gives a rough picture of body composition, which weight alone cannot show.

The US Navy method

The US Navy method estimates body fat from height and a small set of girth measurements, using base-10 logarithms. All measurements below are in centimetres:

  • Men: body fat % = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
  • Women: body fat % = 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450

Men measure the waist at the navel and the neck just below the larynx. Women also measure the hips at their widest point. The method was developed for military body-composition screening and tends to agree with laboratory methods within a few percentage points for most people, though errors can be larger at very high or very low body fat levels.

Worked example

A man who is 178 cm tall with a waist of 85 cm and a neck of 37 cm:

  • waist minus neck: 85 - 37 = 48, and log10(48) = 1.6812;
  • height: log10(178) = 2.2504;
  • denominator: 1.0324 - 0.19077 x 1.6812 + 0.15456 x 2.2504 = 1.0595; and
  • result: 495 / 1.0595 - 450 = 17.2 percent body fat.

An estimate around 17 percent falls in the range commonly described as fit for adult men.

How to interpret your result

A circumference formula is a screening estimate, not a body composition measurement. Methods such as DEXA scans, hydrostatic weighing, or air displacement measure body fat far more directly, and even those disagree with each other by a percentage point or two. Tape-based estimates are most useful for tracking your own trend over time with consistent technique, rather than comparing a single reading against someone else's. Typical reference ranges for adults describe essential fat as roughly 2 to 5 percent for men and 10 to 13 percent for women, with athletic, fit, and average ranges above that.

Measurement tips

  • Use a flexible, non-stretch tape and keep it level and snug without compressing the skin.
  • Measure at the same time of day, ideally in the morning before eating.
  • Take each measurement two or three times and use the average.
  • Have someone help with the neck and hip measurements if possible.
  • Track the monthly trend; day-to-day changes mostly reflect food, fluid, and measurement error.

Related calculators

The BMI calculator offers a simpler height-and-weight screening measure. The meal calorie calculator and water intake calculator help with daily nutrition planning, while the one rep max calculator and pace calculator support strength and endurance training.

This calculator does not replace assessment or advice from a qualified healthcare or nutrition professional.

Frequently asked questions

What method does this body fat calculator use?
It uses the US Navy circumference method, which estimates body fat from height plus neck and waist measurements for men, adding the hip measurement for women. The method was developed for military body-composition screening and needs only a tape measure.
How accurate is the US Navy method?
For most people it agrees with laboratory methods such as DEXA within a few percentage points, provided the measurements are taken carefully. Errors tend to be larger at very high or very low body fat levels and when tape placement is inconsistent.
Where exactly do I measure?
Measure the neck just below the larynx, the waist at the navel for men or at the narrowest point for women, and the hips at their widest point for women. Keep the tape level and snug without compressing the skin, and average two or three readings.
What is a typical body fat percentage?
Commonly cited adult reference ranges put essential fat at about 2 to 5 percent for men and 10 to 13 percent for women, fitness-level ranges around 14 to 17 percent for men and 21 to 24 percent for women, and average ranges above that. Athletes often measure lower, and healthy individuals span a wide range.
Why does my result differ from my smart scale?
Smart scales use bioelectrical impedance, which is sensitive to hydration, food, and recent exercise, while the Navy method depends on tape placement. Both are estimates with different error sources, so the same person can get results several points apart. Tracking the trend from one consistent method is more informative than comparing methods.
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