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Body Fat Percentage Calculator

Estimated Body Fat

16.2%

Body Fat CategoryFitness

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Includes your inputs and results for this calculation, plus any additional calculations you've compared.

Good to Know

This is a circumference-based estimate, not a direct measurement — it can be less accurate for people with body types that fall outside the population the formula was originally validated on, including very muscular or very lean individuals. Measurement technique also affects the result meaningfully.

Disclaimer

This calculator provides estimates for informational purposes only and does not constitute financial, medical, legal, or tax advice. Always consult a qualified professional about your specific situation.

How This Calculator Works

Body fat percentage is estimated here using the U.S. Navy Circumference Method, a formula developed for military body composition assessments using only a tape measure — no scale, calipers, or specialized equipment needed. Enter your height, neck, and waist measurements (plus hip measurement if using the female formula), and this calculator estimates your body fat percentage and which standard category it falls into.

This method is widely used precisely because it’s simple and repeatable, but it’s still an estimate based on a statistical relationship between circumferences and body fat, not a direct measurement. More precise methods (DEXA scans, hydrostatic weighing, or skinfold calipers used by a trained professional) exist, but require specialized equipment this calculator can’t replicate.

The Formula

Men:

Body Fat %=86.010×log⁡10(Waist−Neck)−70.041×log⁡10(Height)+36.76\text{Body Fat \%} = 86.010 \times \log_{10}\left(\vA{\text{Waist}} - \vB{\text{Neck}}\right) - 70.041 \times \log_{10}\left(\vC{\text{Height}}\right) + 36.76

Women:

Body Fat %=163.205×log⁡10(Waist+Hip−Neck)−97.684×log⁡10(Height)−78.387\text{Body Fat \%} = 163.205 \times \log_{10}\left(\vA{\text{Waist}} + \vD{\text{Hip}} - \vB{\text{Neck}}\right) - 97.684 \times \log_{10}\left(\vC{\text{Height}}\right) - 78.387

All measurements use the same unit (inches, in the formula’s original published form — this calculator converts automatically regardless of which unit you enter in). Waist\vA{\text{Waist}} is measured at the navel; Neck\vB{\text{Neck}} just below the larynx; Hip\vD{\text{Hip}} at its widest point (women’s formula only).

The result is then compared against the standard body-fat-percentage categories (American Council on Exercise): Essential Fat, Athletes, Fitness, Average, and Obese — the ranges differ between men and women since essential (health-necessary) body fat levels differ by gender.

Worked Example

A male, height 180cm, neck 38cm, waist 85cm:

  1. Converted to inches: height ≈ 70.9in, neck ≈ 15.0in, waist ≈ 33.5in.
  2. 86.010×log⁡10(33.5−15.0)−70.041×log⁡10(70.9)+36.76≈16.2%86.010 \times \log_{10}\left(\vA{33.5} - \vB{15.0}\right) - 70.041 \times \log_{10}\left(\vC{70.9}\right) + 36.76 \approx 16.2\%.
  3. 16.2% falls in the Fitness category for men (14-17%).

Source: U.S. Navy Circumference Method (Hodgdon & Beckett, 1984).

Frequently Asked Questions

How accurate is the Navy body fat method?

It's an estimate based on a statistical relationship between circumference measurements and body fat, developed for military fitness assessments — generally reasonable for most body types, but less precise than direct measurement methods like DEXA scans, hydrostatic weighing, or professionally-administered skinfold calipers. Measurement technique (exactly where and how snugly you measure) also affects accuracy.

Where exactly should I measure?

Neck: just below the larynx (Adam's apple), tape sloped slightly downward at the front. Waist: at the navel, standing relaxed (not sucked in). Hip (women's formula only): at the widest point around the hips and buttocks. Measure snugly but without compressing the skin.

Why does the formula differ between men and women?

Fat distribution differs between men and women (women naturally carry more essential fat, particularly around the hips), so the Navy method uses a different formula and includes a hip measurement for women that isn't needed for men.