Health and fitness
Body Fat Calculator
Your body fat percentage with a tape measure
This body fat calculator only needs a tape measure. Measure your neck, your waist and, if you are a woman, your hips, in inches or centimeters, and we give you an estimate of your body fat percentage.
An estimate for adults. It is not a diagnosis and does not replace advice from your doctor or another health professional.
The key idea
Your scale does not measure fat: a tape measure gets closer
The US Navy method estimates body fat from your height and the circumference of your neck, waist and, for women, hips. A man who is 5 ft 9 in with a 15 in neck and a 33.5 in waist comes out at 16.9%, in the fitness range. Its margin of error is around 3 to 4 points, but it is useful for tracking your progress.
How it is calculated
The US Navy method estimates body fat from body circumferences and height:
Men: 495 / (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
Women: 495 / (1.29579 − 0.35004 × log(waist + hips − neck) + 0.221 × log(height)) − 450
The formula uses centimeters, so if you enter inches we multiply them by 2.54 first. It has a margin of error of about 3 to 4 points compared with methods such as a DEXA scan, but it is useful for tracking your progress. It is an estimate, not a diagnosis.
Worked example
A man who is 5 ft 9 in with a 15 in neck and a 33.5 in waist: about 16.9% body fat, in the fitness range.
Official sources
- Hodgdon y Beckett (1984): Prediction of percent body fat for U.S. Navy men from body circumferences and height, Naval Health Research Center, informe 84-11 · equation for men
- Hodgdon y Beckett (1984): Prediction of percent body fat for U.S. Navy women from body circumferences and height, Naval Health Research Center, informe 84-29 · equation for women
Typical cases
Body fat estimate by waist size
The US Navy estimate for a man 5 ft 10 in with a 15.5-inch neck and a woman 5 ft 5 in with a 13-inch neck and 40-inch hips, by waist.
| Waist | Man | Man: category | Woman | Woman: category |
|---|---|---|---|---|
| 30 in | 7.8% | Athletic | 30.8% | Average |
| 32 in | 12.3% | Athletic | 33.2% | High |
| 34 in | 16.5% | Fitness | 35.6% | High |
| 36 in | 20.2% | Average | 38.0% | High |
| 38 in | 23.7% | Average | 40.3% | High |
| 40 in | 26.9% | High | 42.5% | High |
| 42 in | 29.9% | High | 44.7% | High |
Save or share this table as an image Common questions
Frequently asked questions
What is the US Navy method?
It is a formula from the US Navy that estimates body fat percentage from height and a few body circumferences. Men use neck and waist; women also use hips. It is cheap and easy to repeat, though less precise than a test such as a DEXA scan.
Is it better than BMI?
It gives more information than BMI, because it estimates fat and not just weight. A muscular person can have a high BMI and little fat, and this formula reflects that better. Even so, both are estimates: use them together with the BMI calculator.
What body fat percentage is normal?
For men, the average range is 18 to 24%, and for women, 25 to 31%. Below that are the fitness ranges (14-17% for men and 21-24% for women) and the athletic ranges (6-13% and 14-20%). These are reference ranges used in fitness, not diagnostic criteria.
How do I measure my waist and neck correctly?
Measure your waist level and without squeezing, at the end of a normal breath out: for men, at the navel, and for women, at the narrowest point. Measure your neck just below the Adam's apple. Always measure under the same conditions, because a quarter inch already moves the result.
Why do I get a warning or an odd result?
Almost always it is a measurement taken wrong or in the wrong unit: check that the units menu matches your tape, and your waist has to be larger than your neck. If the result is below 2% or above 70%, the calculator asks you to check your numbers.
What should I do if my percentage is high?
Treat it as an estimate, not a diagnosis. If you also have a large waist or other risk factors, talk to your doctor or a health professional. To change habits, the calorie calculator gives you an idea of what you need each day.
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