The US Navy body fat formula
This method was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 and is still used for military fitness checks. All measurements are in centimeters (the calculator converts inches for you):
Example: a man 178 cm tall with a 40 cm neck and 87 cm waist: waist − neck = 47, log₁₀(47) = 1.672, log₁₀(178) = 2.250. The divisor is 1.0324 − 0.3190 + 0.3478 = 1.0612, and 495 ÷ 1.0612 − 450 = 16.4% body fat, in the fitness range.
How to measure
- Neck: just below the Adam's apple, tape sloping slightly down at the front.
- Waist: men at the navel; women at the narrowest point. Relax, don't suck in.
- Hips (women): around the widest part of the buttocks.
- Keep the tape level and snug but not pressing into the skin. Measure twice and use the average.
| Category (American Council on Exercise) | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese range | 25% and up | 32% and up |
Frequently asked questions
How accurate is the Navy body fat method?
In studies it usually lands within about 3 to 4 percentage points of lab methods such as DEXA or underwater weighing. It's best for tracking your own changes over time.
What is a healthy body fat percentage?
For many adults, roughly 14% to 24% for men and 21% to 31% for women falls in the fitness and average ranges. Athletes are often lower.
Why does the formula for women include hips?
Women typically carry more fat around the hips and thighs, so the hip measurement makes the estimate more accurate.
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