ISO
Isolated Power (ISO) is a measure of a hitter’s raw power. Or, to look at it another way, it measures how good a player is at hitting for extra bases. The simplest way to calculate ISO is to subtract a player’s Batting Average from their Slugging Percentage, which leaves us with a measure of just a player’s extra bases per at bat.
If you prefer, you can also calculate ISO this way:
ISO = ((2B) + (2*3B) + (3*HR)) / AB
ISO = Extra Bases / At-Bats
It takes a long time for a player’s ISO to have predictive power going forward; a sample size of 550 plate appearances is recommended to draw any conclusions. In other words, if Albert Pujols has a .550 ISO two weeks into the season, it’s way too early to expect that to continue.
Context:
Please note that the following chart is meant as an estimate, and that league-average ISO varies on a year-by-year basis. To see the league-average ISO for every year from 1901 to the present, check the FanGraphs leaderboards.
| Rating | ISO |
|---|---|
| Excellent | 0.250 |
| Great | 0.200 |
| Above Average | 0.180 |
| Average | 0.145 |
| Below Average | 0.120 |
| Poor | 0.100 |
| Awful | 0.080 |
Links for Further Reading:
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Any stat that has Mark Reynolds near the top is a joke
The point of the stat is to measure isolated power. It does that just fine you munch
Yea, a power stat that has Reynolds near the top is a joke. A guy who has averaged 35 home runs per year for the last 4 years. Crazy!
ISO is a useless stat in my opinion. Slugging percentage is superior to it in every way. ISO is just like slugging percentage except making the singles not count. Speed also interferes with the stat, because we all know the type of players that hit triples.
Yea I don’t think anyone makes an argument that ISO is better than SLG but it is a useful state to an extent.
PECOTA’s adjusted ISO makes 3Bs count as 2Bs for the very fact you mention; triples are primarily doubles hit by speedy players and not indicators of extra power.
Yeah and the players that hit triples still don’t hit many and rarely hit HR’s so it balances those guys out generally. I always say, “A triples hitter is a singles hitter who got lucky.”