Body fat calculator
The calculator estimates your body fat percentage from your height and your neck, waist and hip measurements, using the formula the US Navy uses to check its personnel. The result is compared with the healthy range for your sex and age.
The formula was developed by Hodgdon and Beckett at the US Naval Health Research Center in 1984 (report for men, for women): they matched circumference measurements against body fat measured by underwater weighing. All you need is a tape measure.
The healthy ranges come from Gallagher et al. (2000): the body fat percentages that correspond to a healthy BMI in adults. They rise with age and are higher in women than in men.
How it works
- Measure with a soft tape after breathing out, without pulling it tight: the neck just below the Adam’s apple; the waist at the navel for men and at the narrowest point for women; the hips at the widest point of the buttocks.
- Enter your sex, age, height, weight and measurements. Only women need the hip measurement.
- Compare the result with the healthy range and measure again every two to three weeks at the same time of day: the trend tells you more than a single number.
The formula
For men: 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450.
For women: 495 ÷ (1.29579 − 0.35004 × log(waist + hip − neck) + 0.221 × log(height)) − 450.
All measurements are in centimeters; log is the base-10 logarithm. Lean mass is your weight minus fat mass: muscle, bone, organs and water.
The formula is accurate to within 3–4 percentage points. Smart scales with bioimpedance also give an estimate rather than a measurement, and theirs shifts with how much you have had to drink. A DXA scan in a clinic measures more precisely.
| Age | Healthy range: women / men |
|---|---|
| 20–39 | 21–32% / 8–19% |
| 40–59 | 23–33% / 11–21% |
| 60–79 | 24–35% / 13–24% |
Frequently asked questions
- What is a healthy body fat percentage?
- At 20–39, 21–32% for women and 8–19% for men; the upper limit rises with age. These are the Gallagher et al. ranges that correspond to a healthy BMI.
- How accurate is the tape-measure method?
- Within about 3–4 percentage points. That is enough to track change if you measure the same way at the same time of day. For an exact figure you need a DXA scan.
- Why do women need a hip measurement?
- Women store more fat on the hips and buttocks, and without that measurement the formula would be less accurate. Men carry most of theirs around the abdomen, so waist and neck are enough.
Further reading
- Visceral fat: why it matters and how to measure it
- Smart scales: what bioimpedance actually measures
- Waist-to-height and waist-to-hip ratio calculator
More calculators: Waist-to-height and waist-to-hip ratio calculator, Water intake calculator, Keto calculator, Caffeine calculator.
This calculator gives an estimate for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.