# Body Fat Calculator

> Estimate body fat percentage from height, neck, waist and (for women) hip measurements with the US Navy circumference equations, plus fat and lean mass.

Category: Health & fitness · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/body-fat-calculator

The US Navy method estimates body fat from a few tape measurements and your height. It needs only a flexible tape and gives fat mass and lean mass alongside the percentage.

Also called: Navy body fat calculator, Body fat percentage calculator.

## Inputs
- Sex (options: Female, Male; default male)
- Units (options: Metric (cm, kg), US (in, lb); default metric)
- Height (default 178)
- Neck (default 38)
- Waist (default 86)
- Hip (default 100)
- Weight (unit kg; default 80)
- Weight (unit lb; default 176)

## Results
- Body fat
- Fat mass (kg or lb)
- Lean mass (kg or lb)

## Formula

```
Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76;  Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387  (all in inches)
```

Where:
- waist, neck, hip: circumferences in inches (cm ÷ 2.54)
- height: standing height in inches

## Worked example
1. Convert to inches: height 178 ÷ 2.54 = 70.08, neck 14.96, waist 33.86; waist − neck = 18.90.
2. 86.010 × log10(18.90) = 86.010 × 1.2765 = 109.79.
3. 70.041 × log10(70.08) = 70.041 × 1.8456 = 129.27.
4. %BF = 109.79 − 129.27 + 36.76 = 17.3%. Fat mass = 80 × 0.173 ≈ 13.8 kg; lean mass ≈ 66.2 kg.

**Result:** A man 178 cm tall with a 38 cm neck and 86 cm waist has an estimated 17.3% body fat: about 13.8 kg of fat and 66.2 kg of lean mass at 80 kg.

## What the result means

Use the result to follow a trend: measure the same way, at the same time of day, every few weeks. A change of a percentage point or two between single measurements is within the method’s error. Waist size on its own is also a useful health marker.

## Assumptions and limits
- US Navy circumference equations (Hodgdon and Beckett, Naval Health Research Center, 1984), developed on adult military personnel.
- Measurements taken with a non-stretch tape, snug but not compressing the skin.
- For an individual, results can differ from laboratory methods (such as DXA) by several percentage points.
- Less reliable for very lean, very muscular or very large bodies, older adults and pregnancy.
- Not a diagnosis; there is no single agreed set of healthy body-fat cut-offs, so none is shown.

## Questions

### Is this the same as the Army tape test?

The Navy two- and three-site equations were used by several US services, but the US Army replaced its tape test with a waist-to-height ratio in July 2026. See the Army Body Composition Calculator for the current Army check.

### Why do women need a hip measurement?

Women carry more fat around the hips and thighs, so the female equation adds the hip circumference to improve the estimate.

## Sources
- [LibreTexts: The U.S. Navy body fat estimation formula](https://med.libretexts.org/Courses/Irvine_Valley_College/Physiology_Labs_at_Home/03:_Anthropometrics/3.02:_Part_B-_Circumference_Measures/3.2.04:_Part_B4-_The_U.S._Navy_body_fat_estimation_formula)

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- [Army Body Composition Calculator](https://calculators.geekmidst.com/calculators/army-body-fat-calculator)
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_This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/body-fat-calculator