Slobiq Health / Body and shape / Body fat calculator
Body fat calculator
Measure your neck and waist (and hips if you are a woman) with a tape and enter them with your height.
These are general estimates, not medical advice, and they do not replace a doctor, dietitian or trainer. If you are pregnant, under 18, have a health condition or take medication, talk to a professional before changing your diet or training.
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About this tool: Body fat calculator
Body fat percentage says how much of your weight is fat. It tells you more than the scale or BMI, because two people of the same weight can have very different shapes. This calculator uses the circumference method developed for the US Navy by Hodgdon and Beckett in 1984, which needs only a tape measure.
It is a rough estimate. The typical error is about 3 to 4 percentage points, and it depends on measuring the same way every time: relaxed, tape snug but not tight, at the same time of day. Use it to follow the trend rather than to judge one number. It is not suitable during pregnancy.
Formula
Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.221 × log10(height)) − 450. All lengths in cm.
Worked example
A man, 180 cm tall, neck 38 cm, waist 85 cm and 80 kg: body fat about 16.1%, so about 12.9 kg of fat and 67.1 kg of lean mass. A woman, 165 cm, neck 33, waist 70, hips 98 cm and 62 kg: about 25.9%.
Sources and accuracy
- Formulas and sources last reviewed
- Accuracy
- A rough guide only. Typical error of this method is several percentage points or kilograms, so look at the trend over time, not a single number.
Sources and accuracy
Frequently asked questions
Where exactly do I measure?
Neck below the larynx, waist at the navel after a normal breath out, hips at the widest point of the buttocks. Do not pull the tape tight.
Why does my result differ from a smart scale?
Different methods have different errors. Smart scales are sensitive to hydration, so compare readings from the same method over time.
What is a healthy body fat level?
It depends on age and sex. The categories shown are common fitness ranges, not medical diagnoses. Ask a doctor about your own health.