Isolated power

In baseball, isolated power or ISO is a sabermetric computation used to measure a batter's raw power. One formula is slugging percentage minus batting average.

${\displaystyle ISO=SLG-AVG}$

${\displaystyle ={\frac {{\mathit {TB}}-H}{AB}}}$

${\displaystyle ={\frac {({\mathit {1B}})+(2\times {\mathit {2B}})+(3\times {\mathit {3B}})+(4\times {\mathit {HR}})}{AB}}-{\frac {H}{AB}}}$

${\displaystyle ={\frac {({\mathit {1B}})+(2\times {\mathit {2B}})+(3\times {\mathit {3B}})+(4\times {\mathit {HR}})-({\mathit {1B}}+{\mathit {2B}}+{\mathit {3B}}+{\mathit {HR}})}{AB}}}$

${\displaystyle ={\frac {({\mathit {2B}})+(2\times {\mathit {3B}})+(3\times {\mathit {HR}})}{AB}}}$

The final result measures how many extra bases a player averages per at bat. A player who hits only singles would thus have an ISO of 0. The maximum ISO is 3.000, and can only be attained by hitting a home run in every at-bat.

The term "isolated power" was coined by Bill James, but the concept dates back to Branch Rickey and his statistician Allan Roth.¹