IsoP

From SoSH

IsoP (Isolated Power) is used to determine how much raw power a player has. Players like Adam Dunn and Wily Mo Pena have high IsoP despite their low batting average because of their raw power. It is a extremely useful tool when evaluating and projecting prospects.

This statistic was conceived by Branch Rickey and Al Roth in the 1950's. It is formulated by subtracting batting average from slugging percentage.

According to FanGraphs, good IsoP is greater than .290, average IsoP is between .210 and .290, and bad IsoP is less than .210. The league average is ~.275.

Example

Sadaharu Oh smashed 55 home runs in 1964 setting Japan's single-season home run record [since tied by Tuffy Rhodes in 2001 and Alex Cabrera in 2002]. However, using the IsoP formula we see that his record breaking year was not his most powerful. In 1974, 10 years after his record breaking season, he posted 49 home runs and an IsoP .029 points higher than his 1964 mark. Here is why:

1964: 55 HR, 24 2B, 0 3B, 472 AB
1974: 49 HR, 18 2B, 0 3B, 385 AB

As you can see, he almost matched his power numbers in 87 less at-bats.