Body Fat Calculator

Method, assumptions & sources

Who this is for

Adults aged 20 or older, outside pregnancy and breastfeeding; educational estimates for generally healthy adults.

How it works

Circumference method uses base-10 logarithms and inches: male BF% = 86.010 log10(abdomen−neck) − 70.041 log10(height) + 36.76; female BF% = 163.205 log10(waist+hip−neck) − 97.684 log10(height) − 78.387. BMI-derived method: BF% = 1.20 BMI + 0.23 age − 10.8 sex − 5.4 (male sex=1, female=0).

Keep in mind

• Body fat is estimated, not measured. Tape technique and population differences matter.
• No fitness classification or military compliance decision is generated. Outputs outside 0–75% are rejected instead of clamped into a believable result.

Sources

• Naval Postgraduate School: circumference body-fat equations and units (opens in a new tab)
• Deurenberg et al. (1991): adult BMI-derived body fat (opens in a new tab)