How to measure
- Neck: just below the larynx, tape sloping slightly down.
- Waist: men at the navel; women at the narrowest point.
- Hip (women): at the widest point.
Keep the tape snug but not compressing, on bare skin, after breathing out.
The formula behind the result
The Navy method uses a logarithmic formula on your circumference measurements (all in inches):
- Men: 495 ÷ (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450
- Women: 495 ÷ (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.221×log₁₀(height)) − 450
Worked example: a man with a 34" waist, 15" neck, and 70" height gets 495 ÷ (1.0324 − 0.19077×log₁₀(19) + 0.15456×log₁₀(70)) − 450 ≈ 11.1% body fat, landing in the "Athlete" category below.
Where this method comes from
These equations were developed by researchers Hodgdon and Beckett at the US Navy's Naval Health Research Center in 1984, and validated against hydrostatic (underwater) weighing — at the time the reference standard for body composition — in active-duty personnel.
Healthy body-fat ranges
- Women: Athletes 14–20% · Fitness 21–24% · Average 25–31% · Higher 32%+
- Men: Athletes 6–13% · Fitness 14–17% · Average 18–24% · Higher 25%+
Why body fat beats the scale
Two people at the same weight can look completely different depending on muscle vs fat. Tracking body-fat % shows whether you're recomposing — losing fat while keeping muscle — even when the scale barely moves.
Limitations
Tape-measure methods are estimates, typically within about 3–4 percentage points of a DEXA scan for most body types, but less reliable at the extremes of leanness or body size. Measuring at the same time of day, under similar hydration, matters more for tracking trends than any single reading.