Fitness · 5 min read
How to Estimate Body Fat
Navy circumferences — and what the percentage is not
The U.S. Navy method estimates body-fat percentage from tape measurements and height. This tutorial walks through the sex-specific log formulas, a 175 cm / 84 cm waist / 38 cm neck worked example, and a category scale you can try with sliders. Navy %BF is a circumference estimate, not a diagnosis or a DEXA scan.
Written by the My Calculator Stack editorial team. About our methods
Navy body-fat percentage is a screening estimate from tape measurements, not a clinical body-composition test or a medical diagnosis. Tape placement and posture change the result. Talk to a qualified clinician if you need an assessment.
1.What Navy body fat is
The Navy method estimates percent body fat from circumferences and height, not from a scan of tissue. Measure waist at the navel, neck just below the larynx, and (for the female formula) hips at the widest point. The result is an estimate. DEXA, hydrostatic weighing, and similar methods can differ by several percentage points. Treat the number as a screen, then talk to a qualified clinician if you need a diagnosis or a care plan.
2.The formula
Both sexes use %BF ≈ 495 / D − 450, with a different D. Measurements are in centimeters (waist w, neck n, hip p, height h). Male: D = 1.0324 − 0.19077 log₁₀(w − n) + 0.15456 log₁₀(h). Female: D = 1.29579 − 0.35004 log₁₀(w + p − n) + 0.221 log₁₀(h). US customary inputs convert first: inches × 2.54 → cm. After that conversion the same formulas apply. Waist must be larger than neck (male) so the log argument stays positive.
\[ \begin{aligned}D_{\mathrm{male}} &= 1.0324 - 0.19077\log_{10}(w-n) + 0.15456\log_{10}(h) \\\%\mathrm{BF} &= 495 / D - 450\end{aligned} \]
3.Worked example
Take a metric male, height 175 cm, waist 84 cm, neck 38 cm — the same defaults as the body-fat calculator. Then w − n = 46, log₁₀(46) ≈ 1.6628, and log₁₀(175) ≈ 2.2430. D = 1.0324 − 0.19077×1.6628 + 0.15456×2.2430 ≈ 1.0619. %BF = 495 / 1.0619 − 450 ≈ 16.2%. Hip circumference is unused in the male equation. With the female formula and the default 95 cm hip, the same size inputs give a different percentage because D changes.
\[ \%\mathrm{BF}=495/1.0619-450\approx 16.2 \]
4.Circumference playground
Switch Metric/US and male/female, then move height, waist, neck, and (when female) hip to see %BF update and the marker travel across screening bands. The bands are a coarse adult screen, not a clinical classification. This is a teaching widget — no favorites, no full calculator chrome. Open the body-fat calculator when you want the standalone tool.
Inline playground
Body fat
16.2 %
Category: Fitness
495 / 1.0619 − 450 ≈ 16.2
Screening aid only — Navy %BF is a circumference estimate, not a clinical body-composition test or a medical diagnosis.
Open the full body-fat calculator →5.Open the full calculator
The body-fat calculator uses the same Navy equations, the same 175 cm / 84 cm waist / 38 cm neck example, and the same screening disclaimer, with How it works, FAQ, and related fitness tools on one page. Browse other fitness calculators if you need BMI, BMR, or calorie estimates next.
Try it yourself
Open the related calculator and put these formulas to work.