Body fat calculator
Using a few tape measurements, this works out your body fat with the US Navy method and compares it with the healthy ranges for your age and sex.
Your details
Neck: just below the Adam’s apple. Waist: at the belly button for men, the narrowest point for women. Hips: the widest point.
Your body fat estimate
30.8%
In the typical range
- Typical range for your age21% to 33%
- Fat, roughly3 st 4 lb
- Everything else7 st 4 lb
That sits inside the range researchers found for healthy adults of your age and sex. Tape methods can be 3 to 4 points out either way, so treat it as a ballpark.
The working
The US Navy formula
Researchers at the US Naval Health Research Center built this in 1984 by comparing tape measurements with underwater weighing. The sum uses logarithms of your measurements in centimetres:
- Women: 495 ÷ (1.29579 − 0.35004 × log(waist + hips − neck) + 0.221 × log(height)) − 450
- Men: 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
A 35 year old woman at 5 ft 5 in with a 13 in neck, 31 in waist and 39 in hips comes out at about 31%, inside the typical 21% to 33% range for her age.
The ranges
Typical healthy ranges by age
| Age | Women | Men |
|---|---|---|
| 20 to 39 | 21% to 33% | 8% to 20% |
| 40 to 59 | 23% to 34% | 11% to 22% |
| 60 and over | 24% to 36% | 13% to 25% |
These come from a 2000 study by Dympna Gallagher and colleagues, who matched body fat to the healthy BMI range in 1,626 adults. Women naturally carry more fat than men, for hormones and pregnancy.
Read with care
What this cannot tell you
- AccuracyTape methods are usually within 3 to 4 percentage points of a lab test.
- Very lean or very largeThe formula is least reliable at the extremes.
- Where it isIt cannot tell fat under the skin from fat around the organs.
Questions
Common questions
How accurate is the US Navy body fat method?
For most adults it lands within about 3 to 4 percentage points of a DEXA scan. Measuring carefully, twice, makes the biggest difference.
What is a healthy body fat percentage for a woman?
About 21% to 33% for women aged 20 to 39, rising slightly with age. Very low body fat can disrupt periods and bones.
Why do I need my hips if I am a woman?
Women tend to store more fat on the hips and thighs, so the women’s formula includes them to stay accurate.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for US Navy men from body circumferences and height. Naval Health Research Center report 84-11, 1984
- National Academies: body composition in the military services, standards and methods
- Gallagher D et al. Healthy percentage body fat ranges. Am J Clin Nutr 2000
Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.
If your weight is on your mind
Talk to your GP if your weight has changed a lot without trying, or if it is worrying you. If food or your body feels hard to think about, Beat has a free helpline on 0808 801 0677 (England, weekdays 3pm to 8pm).
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