The Strike Zone Is Shrinking. Here’s How.

With the appearance of the ABS problem system, the definition of the strike zone has been laid out with new precision. MLB defines the brand new ABS zone as follows: “The strike zone shall be a two-dimensional rectangle that’s set in the course of residence plate with the sides of the zone set to the width of residence plate (17 inches) and the highest and backside adjusted primarily based on every particular person participant’s peak (53.5% of the batter’s peak on the high and 27% on the backside).” That’s a change from the way in which that the strike zone had been understood since 1996. Per MLB.com, that zone was “the realm over residence plate from the midpoint between a batter’s shoulders and the highest of the uniform pants – when the batter is in his stance and ready to swing at a pitched ball – and a degree slightly below the kneecap. As a way to get a strike name, a part of the ball should cross over a part of residence plate whereas within the aforementioned space.” These two zones are totally different, clearly, and it’s affordable to imagine that they’d have totally different styles and sizes. However how totally different?

Earlier than the season, estimates of how the zone would possibly change ball and strike calls abounded. We’ve heard anecdotally that pitchers assume it’s smaller, and that hitters assume it’s taller. However I haven’t seen any research that try to measure it empirically, so I set out to take action.

I’m going to bore you with loads of math on this article, so let’s begin with a couple of photos earlier than we dive into the small print. I measured a 50% known as strike chance border, normalized by participant peak, utilizing 2025 and 2026 information. The zone has gotten decrease and smaller:

That zone considers righties and lefties collectively. Break it down by handedness, and also you get an analogous end result:

The upshot is that the strike zone has shrunk by round 14 sq. inches for a 6-foot tall batter, from roughly 454 sq. inches to 439 sq. inches. This discovering matches the route of the end result that MLB anticipated to see earlier than the season, if not the exact magnitude. Of their ABS explainer, they approximated the strike zone in 2-2 counts as being 449 sq. inches with the outdated human-called strike zone and 443 sq. inches with the brand new ABS zone.

Now that I’ve given you my top-line findings, let’s get into the methodology. First, I took all of the pitches that had been known as balls or strikes throughout the 2025 and 2026 seasons. I solely thought-about batters who appeared in each seasons in order that I might use their official measured peak; I used their official peak in 2026 for each years to make sure a constant pattern. Then, for every pitch in every year, I normalized vertical location by peak. In different phrases, a 3-foot excessive pitch thrown to a 6-foot tall batter would obtain a price of three/6 or 0.5, whereas a 3-foot excessive pitch thrown to a 7-foot tall batter would obtain a price of three/7. On this means, I produced a height-normalized type of measurement that’s constant between the previous two years, somewhat than utilizing relative distance from a rulebook outlined strike zone. This let me examine like for like — not the realm of the strike zone relative to the rulebook in every year, however the true (height-normalized) dimension of the zone in every year. That is particularly vital as a result of the precise definition of the zone and the way in which the zone known as haven’t all the time correlated completely; in truth, regardless of no change within the rulebook zone, adjustments in umpire analysis have moved the strike zone borders round lately.

I took all of the normalized pitch places in my remaining pattern, after which I additional restricted it by time. I used solely pitches that had been thrown by way of April 25, 2025 final season, and thru April 25, 2026 this season. I’m undecided whether or not there are any hidden calendar results to strike zone dimension, however I didn’t need to take any possibilities; this technique depends on evaluating a like zone, and this time restriction nonetheless gave me loads of information. In spite of everything, the limiting issue right here is the truth that the 2026 season remains to be incomplete, and I haven’t dropped any of that information.

With these known as balls and strikes in hand, I reworked the person calls right into a chance distribution utilizing Nadaraya-Watson kernel regression. In layman’s phrases, it is a bin-and-smooth method. It really works by making a grid, 121×121 on this case, after which inserting every pitch into these bins. It then smooths every pitch’s location utilizing a Gaussian filter and calculates the smoothed called-strike chance in every zone. These called-strike chances are used to create the frontier of the 50% called-strike-probability zone, which I’m utilizing to outline “the strike zone” for this examine. I used the 50% called-strike price because the border as a result of that matches the on-field expertise of the strike zone. For every thing inside this border, an umpire is extra doubtless than to not name a strike. For every thing exterior it, they’re extra doubtless than to not name a ball. Given the inherent uncertainty of the zone as known as by people with occasional robotic help, I feel it is a definition that comes closest to matching how the zone feels to gamers. As a bonus, it’s additionally the usual definition utilized by many seminal research of the strike zone.

Utilizing this methodology, I estimated the dimensions and form of the strike zone previously two seasons. For instance, the highest of the strike zone for a 6-foot batter in 2025 was roughly three ft, 5.5 inches. The highest of the strike zone for a 6-foot batter in 2026 has been roughly three ft, 4.5 inches. The underside of the zone for that 6-foot batter was roughly one foot, six inches in 2025; it’s been roughly one foot, 5.5 inches in 2026. There was no significant change within the width of the strike zone, as you’d count on; that’s outlined by the width of residence plate, which has not modified.

To find out whether or not these adjustments had been statistically vital, I calculated bootstrapped confidence intervals. To do that, I broke my pattern out by sport after which picked video games at random, with alternative, to kind new samples for each years. I repeated this course of 100 occasions. I took the two.Fifth-percentile and 97.Fifth-percentile outcomes of the bootstrap to kind confidence intervals, each for the dimensions of the zone and the change within the dimension of the zone. These outcomes are as follows (reported for a 6-foot batter):

I interpret this as saying the next: The highest of the strike zone is decrease. The underside of the strike zone can be decrease, although by much less. The width of the zone could also be very barely smaller, although it’s exhausting to say. The full space of the strike zone has declined, doubtless by between eight and 22 sq. inches, someplace between 2% and 5% of the entire strike zone space.

One other type of evaluation proved tougher: figuring out the altering form of the zone in numerous counts. There’s a two-fold drawback right here. First, the pattern sizes of the uncooked pitches thrown in every depend are far smaller than they’re for the general inhabitants. Second, we’re in search of zones of the plate the place strikes are known as roughly 50% of the time in order that we are able to carry out boundary evaluation, however batters don’t take a variety of 50/50 balls in sure counts. Search for a cluster of pitches in a 1-2 depend that didn’t produce a swing and but had a 50% likelihood of being known as a strike, and also you’re going to be in search of some time. Batters don’t take these pitches.

Nevertheless, I used to be in a position to cobble one thing along with just a little assist from our in depth library. The PitchingBot mannequin produces estimates of the chance of a swing for each pitch. I used these estimates to create an inverse chance weighting for every pitch. The much less doubtless a given depend/location/pitch sort mixture was to result in a take, the extra I weighted it in our pattern. This statistical methodology corrects for the sampling bias inherent in solely pitches {that a} batter took.

This methodology produced two attention-grabbing takeaways. First, the strike zone in three-ball counts hasn’t actually modified, even whereas every thing else has shrunk. Umpires are in truth calling a barely bigger strike zone in counts with three balls, although it’s statistically indistinguishable from the 2025 zone in the identical counts. Second, the outdated impact of umpires tightening the strike zone in two-strike counts is vanishing. In zero-strike counts, the 2026 strike zone is 8% smaller than the 2025 strike zone. In two-strike counts, the 2026 zone is 1% smaller than the 2025 zone. I’m not assured on this impact dimension, due to the truth that I lower pattern sizes down considerably by bucketing by depend, however I’m assured that an impact exists.

I don’t really feel assured in making any sturdy claims in regards to the downstream results of those adjustments. This examine was arrange significantly to measure the dimensions of the zone, to not take into account how pitcher and batter conduct have modified because of this. That mentioned, it’s actually suggestive that stroll charges have elevated. It’s much more suggestive that the known as strike price for fastballs simply above the borders of the ABS strike zone, 53.5% of a batter’s peak, has declined markedly. In 2025, fastballs thrown inside the width of residence plate and between zero and 4 inches above that 53.5% cutoff had been known as strikes 54.3% of the time. To date in 2026, pitches thrown to that space have been known as strikes 40.8% of the time.

One other attention-grabbing impact: ABS challenges themselves aren’t having a lot impact on the dimensions of the zone. I took all challenged calls and reverted them to the unique umpire name, then re-ran your entire mannequin. The distinction was minimal; utilizing pre-challenge calls, the zone has shrunk ever so barely greater than the measured impact reported on this examine, although not by a statistically vital quantity. The web impact of challenges is sort of small. Right here’s a graphical illustration of the distinction between the as-called zone (utilizing the ultimate end result, post-challenges) and the zone assuming no challenges had been allowed:

None of that is settled science. The zone will proceed to evolve as batters, pitchers, catchers, and umpires alter to the brand new guidelines. The definition of the strike zone isn’t set in stone – clearly so, on condition that the zone was known as in three dimensions final 12 months and known as in two dimensions in 2026. There are significant downstream behavioral implications, too, and I count on league-wide stroll charges to say no as pitchers alter to the brand new strike zone. However to date, pitchers’ reviews of the zone are right: The strike zone, as known as by umpires and the ABS problem system in 2026, covers much less space than it did in 2025.

Appendix A: DataThe information and Python code used to organize the principal evaluation on this article can be found right here. This code covers the strategy for normalizing pitch places, developing normalized pitch plots, measuring the distinction between the 2, bootstrapping confidence intervals, and separating outcomes by handedness. A markdown doc explaining the operate and design of the Python code can be obtainable at that hyperlink. Additional documentation is obtainable as wanted. I’ve disregarded something that makes use of internal-only information, like PitchingBot mannequin values, however I’m pleased to debate particular methodology additional on a one-off foundation.

Appendix B: Additional ReadingI linked to a number of articles in regards to the altering form of the strike zone in 2026 on the high of this text. The next is a extra full bibliography of sources who’ve written in regards to the dimension of the zone within the ABS period:

“How MLB’s Ball-Strike Problem Will Change Baseball,” Peter Abraham, Tim Healey, Alex Speier, John Hancock, and Daigo Fujiwara-Smith, The Boston Globe
“Gamers Say Robotic Umpires Are Shrinking MLB’s Strike Zone,” David Brandt, Jay Cohen, et al., The Related Press
“Every part You Want To Know About The New ABS Problem System,” Anthony Castrovince, MLB.com
“MLB’s Swap to ABS Shrunk Practically Each Hitter’s Strike Zone,” Mike Emeigh and Reddit
“Jose Altuve’s New Strike Zone,” Jarrett Seidler, Baseball Prospectus
“MLB Made a Change That Gamers Say Shrank the Strike Zone,” Jayson Stark, Ken Rosenthal, and Eno Sarris, The Athletic
“ABS Has Shrunk The Strike Zone; Walks Are Spiking As Hitters Strive To Alter,” Cody Stavenhagen, The Athletic
“ABS Problem Charges By Proximity to Border of Strike Zone,” Tom Tango
“Lefties Eat Scorching Canines, Righties Eat Burgers,” Matthew Trueblood, Baseball Prospectus
“Sure, MLB’s Strike Zone Is Shrinking. However Baseball Will Be Higher For It,” Tom Verducci, Sports activities Illustrated
“That is Not Even The Strike Zone’s Ultimate Type,” Bradley Woodrum, Baseball Prospectus