GUIDES · BETSLIP DOCTOR
What does isolated power tell me that slugging percentage does not?
Slugging percentage measures total bases per at-bat. Isolated power (ISO = SLG minus batting average) measures the extra bases beyond the first base credited for each hit, per at-bat.
For Baseball readers comparing a hitter's power statistics · Updated
Slugging counts every credited base
Slugging percentage divides total bases by at-bats. A single is worth one total base, a double two, a triple three and a home run four.
It is a rate that includes singles as well as extra-base hits.
ISO isolates the extra-base portion
Isolated power is slugging percentage minus batting average. Subtracting the one-base-per-hit component leaves the additional bases credited by doubles, triples and home runs per at-bat.
ISO helps answer a narrower question about extra-base power; it is not another name for total bases or a forecast of future performance.
Hypothetical hit lines
Fictional example over ten at-bats: one hitter gets four singles, while another gets two singles and one double. Each records four total bases and a .400 slugging percentage. The first has a .400 average and .000 ISO; the second has a .300 average and .100 ISO.
Related questions
Can two hitters have the same slugging percentage but different ISO?
Yes. Their total bases per at-bat can match even when one gets more of those bases from extra-base hits.
Does ISO count walks?
No. The MLB definition uses extra-base hits per at-bat, or equivalently slugging percentage minus batting average.