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Body Fat Calculator

Free to use, with no sign up. Your entries stay in this browser; calculations run on your device.

Stand upright. Measure neck just below the larynx. For the male formula, measure abdomen at the navel. For the female formula, measure the natural waist and hips at their widest point. Keep the tape level and snug without compressing skin.

US Navy tape estimate

Enter your tape measurements to see an estimate.

Male: % body fat = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.77.

Female: % body fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387.

All formula measurements are in inches and logs are base 10. Centimetres are divided by 2.54 before calculation. NOAA Corps Chapter 16, Navy Standard Formula. Male abdomen must exceed neck; female waist plus hip must exceed neck.

Estimate body fat from BMI and age

This separate adult estimate uses BMI and age, not tape measurements. Enter a known BMI or work it out with our BMI calculator. BMI describes weight for height and cannot distinguish muscle from fat.

An estimate from BMI and age

Enter BMI, age and sex for an estimate, not a measurement.

Deurenberg adult estimate: % body fat = 1.20 × BMI + 0.23 × age − 16.2 (male), or −5.4 (female). Deurenberg, Weststrate and Seidell, 1991.

Both methods estimate body fat; neither directly measures it. Tape placement and body shape affect the Navy result. A BMI estimate may be misleading when muscularity differs from the study population. Results outside 0–100% are refused rather than adjusted.

For general information only; not medical advice.

How to use this tool

Choose inches or centimetres and enter the measurements for your selected Navy formula. Use the separate BMI and age form for a second estimate.

Frequently asked questions

Does this measure body fat?

No. The Navy method estimates it from tape measurements, and the Deurenberg method estimates it from BMI, age and sex. Neither is a direct body fat measurement.

Where should I place the tape?

Measure neck just below the larynx. The male formula uses abdomen at the navel; the female formula uses the natural waist and the widest part of the hips. Keep the tape level without compressing skin.

Can I enter centimetres?

Yes. Choose centimetres and the calculator divides every tape measurement by 2.54 before using the inch-based NOAA constants. Changing units converts valid entries.

Why are some measurements refused?

The logarithm needs a positive value. Male abdomen must be greater than neck, and female waist plus hip must be greater than neck. All required measurements must be positive; estimates outside 0–100% also need your entries checked.