Body-fat percentageBody fat %

Body-fat percentage is the proportion of your total body weight made up of fat, with the rest being lean mass (muscle, bone, organs and water). It describes composition in a way that weight or BMI alone cannot.

It matters because two people at the same weight can look and perform very differently depending on how much is fat versus muscle. Tracking it can be more informative than the scale, though every measurement method has meaningful error.

In practice, estimates from calipers, tape formulas, bioelectrical scales and DEXA all vary, so it's best to pick one method and follow the trend rather than fixating on a single exact figure.