Slugging percentage minus batting average — a measure of a hitter's raw extra-base power.
Isolated power strips singles out of slugging percentage to isolate extra bases per at-bat. A hitter with a high batting average but few extra-base hits has a low ISO; a three-true-outcomes slugger can have a modest average and a high ISO.
ISO is a fast way to gauge power independent of how often a hitter reaches base. It pairs naturally with home-run and total-bases research.
ISO frames extra-base and total-bases props: a hitter's power profile against a given pitcher and park is the first filter before the model's projection.
Isolated power equals slugging percentage minus batting average. It represents extra bases per at-bat, so it captures power without rewarding singles.