Body Fat Calculator (US Navy Method)
Estimate your body fat percentage using just a tape measure. The US Navy circumference method needs your height, neck, and waist measurements (and hip for women).
📖 Read the guide: BMI vs body fat percentage
How to measure
- Time of day: measure first thing in the morning before eating or drinking. Bloating in the evening can shift waist size by 1–2 inches.
- Tape: a flexible cloth or fiberglass tape. Pull snug, not tight. The tape should sit flat against the skin without compressing.
- Neck: just below the larynx (Adam's apple). Look straight ahead; don't tuck your chin.
- Waist: men measure at the navel; women measure at the narrowest point of the torso.
- Hip (women only): widest point around the buttocks.
- Repeat: take each measurement twice and average them.
ACE body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Formula
Men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Both formulas expect measurements in inches; metric inputs are converted internally.
Limitations
The US Navy method is one of the simplest body composition tests but not the most accurate. It assumes typical fat distribution and underestimates fat in very muscular or very lean individuals. For more precision, look into DEXA scans (most accurate, ~$50–150), bod pod testing, or hydrostatic weighing. Skin-fold caliper testing by a trained technician is also more accurate than tape-only methods.
This calculator is for general fitness reference and is not medical advice. Consult a healthcare provider before making major changes to diet or exercise.