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Body Fat Calculator
Body fat estimate
Precision Body Composition Protocol
About the Body Fat Calculator
This calculator estimates your body fat percentage from simple tape measurements using the US Navy circumference method. It needs no special equipment, so it is a practical way to track body composition alongside your weight.
How to use the Body Fat Calculator
- Select Male or Female.
- Enter your Age, Weight (kg) and Height (cm).
- Measure your Neck just below the larynx and your Waist at the navel (men) or the narrowest point (women). Women also measure the Hips at the widest point. Use centimetres and keep the tape snug but not tight.
- Press the calculate button to see your body fat percentage, category and a breakdown of fat mass versus lean mass.
Formula and method
Men: %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
All measurements are in centimetres.
Worked example
A man who is 180 cm tall with a 38 cm neck and a 90 cm waist: waist − neck = 52 cm. 495 ÷ (1.0324 − 0.19077 × 1.716 + 0.15456 × 2.255) − 450 = 495 ÷ 1.0536 − 450 = about 19.8% body fat.
Tips
- Measure at the same time of day, ideally in the morning before eating, and take each measurement twice.
- Do not pull the tape tight into the skin; that lowers the reading.
- Circumference methods have a margin of error of a few percentage points. Track the trend over weeks rather than a single number.
- DEXA scans and hydrostatic weighing are more accurate if you need clinical precision.
Frequently Asked Questions
Roughly 10 to 20 percent for men and 18 to 28 percent for women is considered healthy for most adults, with athletes often lower. The ideal range varies with age and goals.
It is usually within about 3 to 4 percentage points of laboratory methods for average builds, but less reliable for very lean, very muscular or very heavy people.
Height is part of the formula. Weight is used to split your body into fat mass and lean mass once the percentage is known.