On An Umpire’s Strike Zone

Baseball is subjective. As much as we look at numbers and data and try to interpret it in order to predict an outcome, what ends up happening in single samples is often decided by different interpretations of an imaginary box that hovers over home plate.

Just look at the fluctuations in success and failure an average batter enjoys or suffers depending on the balls and strikes count. Not only do we depend on an umpire’s interpretation of a strike zone, but we also depend on the pitcher’s, batter’s, and as we’ve recently discovered, the catcher’s interpretation of that interpretation. In many ways, baseball is a game of Socratic shadows.

Despite all this subjectivity at play, it doesn’t stop us from jumping up out of our seats in pure anger at an umpire’s perceived lack of competence. While the more discerning fans among us may take into account that our perspective as given to us by the television broadcast is often as faulty as the ones being offered by the outdated minds in the play-by-play booth, several of us rush to a Pitch FX website the moment a questionable call is made to see definitive proof of where the pitch landed.

It’s worth emphasizing the two warnings provided by Brooks Baseball for both the normalized and non-normalized Pitch FX strike zones that they provide.


These parameters are variable and should not be taken as gospel (or any other works of Holy Writing, including Torah or Qu’ran). The outside edges of the strikezone are then drawn to specifications corresponding to an average umpire’s strikezone.


Because of variable batter height, this may not provide a completely accurate picture of an Umpire’s Strikezone in the Vertical Axis. The outside edges of the strikezone are then drawn to specifications corresponding to an average umpire’s strikezone.

In other words, this data needs to be taken with a grain of salt, as it’s far from definitive, and also depends on calibration differences from ballpark to ballpark.

It’s also worth remembering that an umpire’s subjectivity consistently creates a different strike zone for right handed and left handed batters. Beyond The Box Score put together some excellent research on this back in 2009.

Because umpires are positioned to see the inside pitch, they call balls and strikes more consitenly on the inside versus the outside.   Besides the lack of consistency on the outside part of the plate,  the strike zone shifts inside between 0.2 to 0.4 feet depending on the batter’s handedness.

Consider the following charts that Beyond The Box Score created to further emphasize their findings:

The glaring and consistent differences between strike zones for right handed batters and left handed batters sparked an interesting conversation held on Twitter between Mike Fast of Baseball Prospectus and Dan Brooks, the owner and operator of Brooks Baseball. The end result of which is the cheekily titled Fastmap Strikezone Maps.

These plots show the strikezones that Umpires actually call. The dashed lines around the black border show the typical deviations for LHH and RHH.

Here are what the strike zones look like for called balls and strikes:

Robot umpires won’t have a place in baseball for the foreseeable future, so the best that we can hope for as fans of America’s pastime is a consistent strike zone. While it may not be by the letter of the law, consistencies do exist in the separate subjective strike zones given to right handed and left handed batters individually.

And so, this latest addition to Brooks Baseball is a welcome one, and will at least make our criticisms of an umpire’s strike zone a little more accurate. While it’s still not perfect, now, when we burn an umpire in effigy or claim an obvious bias against the New York Yankees, we have a little more realistic evidence based on practice, not just theory, to justify our claims.

Thanks Mr. Brooks. Major League Baseball umpires will now be placing bullets in your mailbox.