Estimated from circumferences. Tape-measure based.
Source: Hodgdon & Beckett, US Navy (1984).
What does body fat percentage mean?
Body fat percentage is the proportion of your total body weight that is made up of fat tissue. The remainder, bones, muscles, organs, water, and other lean mass, makes up your fat-free mass. Understanding your body fat percentage gives a clearer picture of body composition than weight or BMI alone, since two people at the same weight can have very different amounts of fat versus muscle.
The US Navy circumference method, developed by Hodgdon and Beckett in 1984, estimates body fat using logarithmic equations based on neck, waist, and (for women) hip circumference, along with height. For men: %BF = 86.01 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76. For women, the hip measurement is included in the formula.
The method has a standard error of approximately ±3–4% when compared to DEXA scanning. It works best for people of average build. Very lean individuals are often overestimated; very obese individuals may be underestimated. For accurate measurements, use a flexible tape, measure at the same time of day (morning, before eating), and take two readings per site, averaging them.
Body fat is metabolically active, visceral fat (around organs) is particularly harmful and contributes to insulin resistance, inflammation, and cardiovascular risk. Reducing body fat, especially in the abdominal area, improves nearly every metabolic marker.
Reference ranges
| Category | Women (%) | Men (%) |
|---|---|---|
| Essential fat | 10 – 13 | 2 – 5 |
| Athletes | 14 – 20 | 6 – 13 |
| Fitness | 21 – 24 | 14 – 17 |
| Acceptable / healthy | 25 – 31 | 18 – 24 |
| Obese | ≥ 32 | ≥ 25 |
When should you see a doctor?
Consult a doctor if your estimated body fat is above the obese threshold, if you have noticed rapid unexplained changes in body composition, or if you want a more precise measurement. A clinician can arrange DEXA scanning, hydrostatic weighing, or air displacement plethysmography for greater accuracy. High visceral fat specifically warrants a metabolic workup including fasting glucose and lipid panel.