Body Fat Calculator — US Navy Circumference Method

Estimate your body-fat percentage from tape measurements using the published US Navy equations.

  • Nutrition
  • 2 cited sources
  • Runs in your browser
Sex
Unit system

Your estimated body fat

17.2%

Realistic range: about 13.7% – 20.7%

The US Navy circumference method carries a ±3–4 percentage-point error band against laboratory methods, so treat the single figure as the centre of the range above. Measured consistently, it tracks change over time well — that trend is the useful number.

Methodology

This tool implements the US Navy circumference method exactly as published by Hodgdon and Beckett (Naval Health Research Center, 1984), working in centimetres with base-10 logarithms:

SexEquation (% body fat)
Men495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450

The equations estimate body density from the circumference measurements, then convert to percent fat. In the original validation they correlated about r = 0.90 with underwater weighing.

Measuring well matters more than anything else: use a flexible, non-stretch tape, snug against the skin without compressing it. Neck: just below the larynx, tape sloping slightly down to the front. Waist: at the navel for men; at the narrowest point for women. Hips (women): at the widest point. Take each measurement two or three times and average.

Interpreting your result

Every result carries the method's published error band of roughly ±3–4 percentage points, which is why we display a range rather than pretending to single-decimal accuracy. A reading of 18% really means "most likely somewhere between about 14.5% and 21.5%".

Where the method shines is trend tracking: measurement error is fairly consistent for a given person, so changes over weeks and months are much more trustworthy than any single absolute number.

Limitations

  • Circumference methods assume typical fat-distribution patterns; very muscular necks, or fat carried atypically, push results off in predictable directions.
  • Hydration, food timing and tape tension all move readings — measure under consistent conditions, ideally first thing in the morning.
  • The equations were derived from US Navy personnel and generalise reasonably, but not perfectly, to other populations.
  • No field method replaces clinical assessment where body composition has medical implications.

Sources

Pull the receipts — 2 cited sources

FitTools · sources

  1. 01 Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Naval Health Research Center, Report No. 84-11, 1984
  2. 02 Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. Naval Health Research Center, Report No. 84-29, 1984

Every formula cited ✓

Frequently asked questions

How accurate is the Navy body fat method?
In the original validation it correlated about r = 0.90 with underwater weighing, with a standard error of roughly 3 to 4 percentage points. Treat your result as the centre of a band, not an exact figure — we show that band with every estimate.
How do I take the measurements?
Use a flexible tape, snug but not compressing the skin. Measure the neck just below the larynx, the waist at the navel for men or the narrowest point for women, and (for women) the hips at the widest point. Average two or three readings for each site.
What is a healthy body-fat percentage?
Typical healthy ranges are roughly 10–20% for men and 18–28% for women, varying with age and athletic goals. Essential fat sits around 3–5% for men and 10–13% for women; going near those floors is neither necessary nor advisable for most people.
Why does the formula only use a few measurements?
The Navy method was designed to estimate body density from quick field measurements that anyone can take with a tape. It trades some accuracy for practicality — laboratory methods such as DEXA are more precise but far less accessible.
Why does my result differ from my smart scale?
Bio-impedance scales estimate body fat from electrical conductivity, which swings with hydration, food and skin temperature. Neither method is exact; what matters most is tracking the trend using the same method under the same conditions.

Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.

Last reviewed:

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