SoSH Glossary: Isolated Power

Baseball is filled with statistics, rules, and archaic terms that can often form what sounds like a foreign language.The Sons of Sam Horn glossary provides a better understanding of these terms through straightforward definitions, clear explanations, and examples pulled straight from the baseball world. If there is anything you would like us to add to our glossary, please contact us.

Isolated Power

Isolated power (ISO) is a statistic which measures a player’s extra bases per at-bat. ISO displays a hitter’s in-game power by removing singles from the equation. The statistic was created by legendary general manager Branch Rickey and baseball historian Allen Roth. There are four commonly used equations that can be used to find ISO – the first is Rickey and Roth’s original.  

How is it Calculated?

eqn_iso

Things to Consider About ISO

  • ISO is context neutral, meaning that it does not account for league, park, or game situation.
  • While any sample size of isolated power will describe a player’s past performance, it takes approximately 550 at-bats (roughly one season) before ISO becomes predictive.
  • League-average ISO in MLB is around .140, while power hitters’ isolated power is usually .200 and above. The elite power hitters of MLB have ISOs in the high .200s and sometimes even into the .300s.
  • Before making judgments about a hitter’s overall value, it is important to observe a hitter’s other statistics as ISO only looks at one piece of the puzzle.

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