Stat of the Week: Isolated Power (ISO)
This should be a very straightfoward Stat of the Week because it is something you can easily calculate at home without any sort of complex math. This week, we’re talking about Isolated Power (ISO) which measures how good a player is at hitting for extra bases.
You’re likely more familiar with Total Bases (TB) which is a counting stat that picks up on a similar concept. ISO is essentially Slugging Percentage with the singles stripped out.
ISO = (2B+2*3B+3*HR)/AB
A rule of thumb scale puts average ISO around .145 and anything about .200 being great. You read Fangraphs’ write up on the subject here.
I wouldn’t recommend looking at ISO over wOBA or wRC+, but it I would look at it in addition to those two metrics. It can provide you a nice piece of information about how frequently a guy hits for extra bases. It contains the same problem that slugging percentage does in that it weighs doubles, triples, and homeruns improperly, but it’s a good way to separate how much of a player’s slugging percentage is driven by a high rate of singles versus real extra base power. It’s also not a particularly predictive stat over a small sample if you’re concerned about that type of thing.
For reference, the top 5 players by ISO from 2012 were: Josh Hamilton, Edwin Encarnacion, Miguel Cabrera, Ryan Braun, and Josh Willingham.