2022 Blogmas Day 6 – Isolated Power

In another day of simpler statistics, Isolated Power (ISO) is derived from slugging percentage. It’s calculated in the exact same way, but ignores singles. Hence, it is isolating the power of a hitter, defined as the rate at which they get extra-base hits.

Let’s go straight to the formulas.

\text{ISO} = \frac{\text{2B} + 2\times\text{3B}+ 3\times\text{HR}}{\text{at-bats}}

Note that we weight things slightly differently than with slugging percentage, because this also gives us:

\text{ISO} = \text{SLG} - \text{BA}.

With today’s ability to track ball speed and angle off the bat, I don’t think ISO has much place in the game. It is certainly an interesting statistic for getting a sense of how much of a player’s hitting is made up of extra-base hits, but I file it away as “fun to look at, but ultimately inconsequential for comparing players.”

A few pieces of trivia:

• The pitcher with the best season ISO, having at least 20 plate appearances, was Lou Sleater in 1957. He had an ISO of .450 due to 3 home runs across 20 at-bats.
• Among qualified players¹As a reminder, this would be 502 plate appearances on the season. in the 21st century, Barry Bonds is number 1, 2, and 3 on the list of highest ISO: .536 in 2001²You may know this as the year he broke the MLB home run record with 73., .450 in 2004, and .429 in 2002.

Continue to Day 7 – Batting Average on Balls in Play

• 1
  As a reminder, this would be 502 plate appearances on the season.
• 2
  You may know this as the year he broke the MLB home run record with 73.