How body-fat is measured
Written by The Kalcule Team · Last updated 18 Αυγούστου 2026
DEXA, Bod Pod, hydrostatic weighing, BIA scales, calipers and circumference equations all estimate fat mass. They disagree with each other. Knowing the method’s error bar is more useful than chasing a single “true” percentage.
Laboratory methods
DEXA, air displacement and underwater weighing are references for research. They still have error, cost money, and are easy to over-interpret to 0.1%.
Field methods
Navy circumferences (this site), calipers and home BIA scales are for trends. BIA moves with hydration. Calipers need a skilled tester. Circumferences need consistent landmarks.
Pick one method and repeat it
Comparing last month’s scale BIA to this month’s DEXA is noise. Use the same protocol, same time of day, every few weeks.
Use the Kalcule calculator honestly
Our body-fat calculator is the Navy method. Read the limitations on that page. It is a tape and some algebra, not a scan.
Συχνές Ερωτήσεις
Comparing body-fat measurement methods.
Multi-compartment lab models sit at the top. For home use, a consistent circumference or caliper protocol beats a cheap BIA scale used casually.
Different algorithms, electrodes and hydration. Believe the trend on one device more than the absolute number.
Optional. Waist, photos and strength often tell you enough.
BMI does not measure fat. It is a different, coarser screening index.
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