Base Sizes (2023 rule change)

Definition

In September 2022, Major League Baseball announced three rule changes that were approved by the league’s Competition committee. The rules were adopted after extensive testing at the Minor League level over a several-year period and with feedback from MLB player and umpire representatives..

One of the rule changes covers the size of the bases, which traditionally have been 15 inches square, but will now be 18 inches square. Home plate remains unchanged.

Though the base-size change may have a modest impact on stolen-base success rate, the modification’s primary goal is to give players more room to operate and to avoid collisions. This is especially key at first base, where fielders will have an extra 3-inch advantage to stay out of harm’s way from the baserunner while receiving throws.

The change will create a 4 1/2-inch reduction in the distance between first and second base and between second base and third, which will likely encourage more stolen-base attempts. The bigger bases could also have the effect of reducing over-sliding, whereby a player loses contact with the bag after sliding through it.