Body Fat Calculator
Estimated body fat using the US Navy method.
Inputs
This calculator gives a general estimate and isn't medical advice. It doesn't account for your individual health history — talk to a doctor before making decisions based on it.
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Formula
Male: 86.010×log₁₀(waist−neck) − 70.041×log₁₀(height) + 36.76; female adds hip to the log term
Circumference measurements at the neck, waist, and (for women) hip are converted through logarithmic US Navy equations to estimate body fat percentage without calipers or scans.
Worked example
A man 175 cm tall with an 85 cm waist and 38 cm neck measures about 23.5% body fat by the US Navy method — a typical 'fitness' range for recreational athletes.
Where this can give the wrong answer
- Female results require a hip measurement; leaving hip at zero or omitting it returns an error instead of a male formula result.
- Results are clamped between 2% and 60% — values outside that range from bad tape placement won't display as implausible extremes.
- The Navy method assumes standard fat distribution; very muscular necks or bloated waist readings (post-meal, poor posture) skew the estimate.
FAQ
- Neck: just below the larynx, tape horizontal. Waist: at the navel level, relaxed, not sucked in. Hip (women): widest point around the buttocks. Consistency matters more than squeezing the tape tight.