Body Fat Calculator
This estimates body fat from a tape measure and your height, using the US Navy circumference equations. It is an estimate: against underwater weighing it was typically within about 3.5 to 4 percentage points.
Source: Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men (Report 84-11) and women (Report 84-29) from body circumferences and height. Naval Health Research Center, San Diego, 1984.; Department of Defense Instruction 1308.3, DoD Physical Fitness and Body Fat Programs Procedures, Enclosure 3. November 5, 2002 (cancelled 2022).; Gallagher D, Heymsfield SB, Heo M, et al. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr 2000;72(3):694-701. (doi:10.1093/ajcn/72.3.694)
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For a quicker central-fat check, see the waist-to-height ratio calculator, or the BMI calculator.
How to measure
Use a flexible tape, snug against the skin but not compressing it. Measure each site three times and use the average.
- Neck: just below the Adam’s apple, with the tape perpendicular to the neck.
- Waist, men: at the navel, level with the floor, at the end of a normal relaxed breath out.
- Waist, women: at the narrowest point, usually about halfway between the navel and the bottom of the breastbone.
- Hips, women only: around the widest part of the buttocks, viewed from the side.
The Navy formulas
All measurements in inches:
- Men: % body fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: % body fat = 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Worked examples
- A man 70 in tall, neck 15 in, waist 34 in: 17.5% body fat
- A woman 65 in tall, neck 13 in, waist 28 in, hips 38 in: 25.9% body fat
How accurate is it?
The equations were built by the Naval Health Research Center in 1984 from 602 men and 214 women whose body fat was measured by underwater weighing. Against that reference, the typical error was about 3.5 percentage points for men and 3.7 for women. In a 2025 study of 1,904 soldiers, tape-measure methods read lower than a DXA scan on average, by several percentage points.
Use the result to track change over time with the same tape and technique, rather than as an exact number. The US military used these equations for decades; in 2022 the Department of Defense stopped prescribing a single equation, and its current standard screens with waist-to-height ratio first.
Healthy body fat ranges
These ranges come from a study that matched body fat to the standard BMI cut-offs in adults of different ages and ancestries. The “Healthy” column is the range that matches a healthy BMI of 18.5 to 25.
White, Black and other adults:
| Age | Below healthy | Healthy | Overweight range | Obesity range |
|---|---|---|---|---|
| Women 20 to 39 | Under 21% | 21% up to 33% | 33% up to 39% | 39% or more |
| Women 40 to 59 | Under 23% | 23% up to 34% | 34% up to 40% | 40% or more |
| Women 60 to 79 | Under 24% | 24% up to 36% | 36% up to 42% | 42% or more |
| Men 20 to 39 | Under 8% | 8% up to 20% | 20% up to 25% | 25% or more |
| Men 40 to 59 | Under 11% | 11% up to 22% | 22% up to 28% | 28% or more |
| Men 60 to 79 | Under 13% | 13% up to 25% | 25% up to 30% | 30% or more |
Asian adults:
| Age | Below healthy | Healthy | Overweight range | Obesity range |
|---|---|---|---|---|
| Women 20 to 39 | Under 25% | 25% up to 35% | 35% up to 40% | 40% or more |
| Women 40 to 59 | Under 25% | 25% up to 35% | 35% up to 41% | 41% or more |
| Women 60 to 79 | Under 25% | 25% up to 36% | 36% up to 41% | 41% or more |
| Men 20 to 39 | Under 13% | 13% up to 23% | 23% up to 28% | 28% or more |
| Men 40 to 59 | Under 13% | 13% up to 24% | 24% up to 29% | 29% or more |
| Men 60 to 79 | Under 14% | 14% up to 24% | 24% up to 29% | 29% or more |
Body fat naturally rises with age at the same BMI, which is why the ranges shift upward. The authors cautioned that the low-end limits are the least certain.
FAQs
What is a healthy body fat percentage?
It depends on age, sex and ancestry. For a white or Black man aged 20 to 39, 8% up to 20% matches a healthy BMI; for a woman of the same age, 21% up to 33%. See the tables above for other ages.
Is the Navy body fat method accurate?
It is a reasonable estimate. Against underwater weighing its typical error was about 3.5 to 4 percentage points, and it tends to read lower than a DXA scan. It is best for tracking your own change over time.
Why do women need a hip measurement?
The women’s equation was developed from waist, hip and neck measurements together, so it cannot be calculated without the hip measurement.