The Rules for Bats, Balls and Gloves

By 4Baseball Staff · November 5, 2026 · 10 min read

What the Official Baseball Rules say about the size, material and treatment of bats, baseballs and gloves, from the 2.61-inch barrel and the pine tar line to the ball's weight and the limits on each glove.

Baseball is played with three pieces of equipment that look simple and are tightly regulated: a wooden bat, a leather-covered ball and a leather glove. The Official Baseball Rules, the book that governs the major leagues, set limits on the length and thickness of the bat, on the weight and circumference of the ball, and on the size and color of the glove. Those limits explain a surprising number of well-known controversies, from the pine tar game of 1983 to corked bats to the crackdown on sticky substances in 2021.

This article walks through the rules for each of the three, explains what each limit is for, and points out the differences between professional equipment and the aluminum bats used at amateur levels. The figures below describe the Official Baseball Rules as of the 2025 season. Rules are revised from time to time, so if a measurement matters for a decision (a purchase for a league, a dispute over an at-bat), check the current rulebook on MLB.com or the rules of the league you play in.

The professional bat: length, diameter and wood

The rulebook's section on the bat says that it must be a smooth, round stick, no more than 2.61 inches in diameter at the thickest part and no more than 42 inches long. In metric terms that is roughly 6.6 centimeters across and 107 centimeters long. In the professional game it must be one piece of solid wood. Laminated or experimental bats are not allowed unless the sport's rules committee has approved them in advance.

Three things follow from that wording.

• There is no weight limit. The rules say nothing about how heavy a bat can be. A hitter may use any weight he can swing, and the weight is a matter of preference and strength. This is different from amateur baseball, where weight is tied to length (see below).
• There is no minimum length. The 42-inch figure is a ceiling. Hitters typically choose bats in the low-to-mid 30s of inches, and the right length depends on the batter's height, reach and style.
• Wood species are not named. The rule says solid wood, not which wood. Ash was the traditional choice, maple became popular in the 2000s, and birch is also used.

The 2.61-inch limit is the number to remember. A thicker barrel would add mass and a bigger hitting surface at the point of impact, which is exactly what the limit prevents. Within that limit, a hitter chooses between a thicker barrel with more wood behind the ball and a thinner, lighter bat that is easier to swing quickly.

A bat may also be cupped, meaning a rounded depression is cut into the end of the barrel to take weight out of the end. The rulebook limits the depth of the cup to one and a quarter inches. A cupped bat has less mass at the end, so it swings more easily without changing its length.

Pine tar and the 18-inch line

The bat's handle can be treated to improve grip. The rulebook permits tape, pine tar, rosin or a similar substance on the handle, but only up to 18 inches from the end of the handle. A bat with a foreign substance past that line is illegal. Pine tar is a sticky resin, and hitters have used it for generations to keep the bat from slipping, especially in cold or wet weather.

The 18-inch rule produced one of the most famous disputes in the sport. On July 24, 1983, at Yankee Stadium, George Brett of the Kansas City Royals hit a home run in the ninth inning to put his team ahead. The Yankees' manager, Billy Martin, pointed out that the pine tar on the bat extended past the legal line, and the umpire ruled the bat illegal and called Brett out, which erased the home run and ended the game. The Royals protested, and the American League's president, Lee MacPhail, overturned the ruling and ordered the game to be resumed from the point of the home run. It was completed on August 18.

MacPhail's reasoning was that the rule was meant to prevent pine tar from staining the ball, not to punish a hitter for gripping the bat, and that the penalty for an excess of pine tar should be removal of the bat, not an out. The rulebook now says that when an umpire finds a bat that does not meet the pine tar rule only after it has been used, the batter is not called out and not ejected. It is one of the clearest examples of a rule's consequences being rethought because a specific game exposed a flaw.

Corked and altered bats

The line between a legal bat and an illegal one is the difference between a solid piece of wood and a modified one. A batter who uses a bat that has been altered, for example by drilling out the barrel and filling it with cork or another material, is out and is ejected from the game. The reasoning is that a hollowed bat can be lighter, letting the hitter swing faster, and the rules treat any alteration meant to improve the distance or the behavior of a batted ball as cheating.

Famous cases are well documented. In June 2003, Sammy Sosa of the Chicago Cubs broke a bat during a game, and the pieces showed cork inside; he was ejected and suspended. Albert Belle was suspended for a corked bat in 1994. Sosa's bat was exposed because it broke; Belle's was examined after an opposing club complained. The wider point is that bats are not routinely inspected, so a corked bat tends to be found only when it breaks or when someone challenges it.

For more on how umpires decide whether to eject a player, see ejections and the umpire-manager argument, and for how the game's crews are trained and assigned, see how umpires are trained, assigned and evaluated.

Bats below the professional level

Professional baseball requires wood, but most amateur baseball does not. High school and college players use metal or composite bats, and the rules for those bats are set by the governing bodies, not by the Official Baseball Rules.

BBCOR stands for batted ball coefficient of restitution, which measures how much energy a ball keeps when it bounces off the bat. The aim of the BBCOR standard, adopted by the NCAA in 2011 and by high school baseball in 2012, was to make a metal bat perform like a wood bat, because earlier aluminum bats sent the ball off faster, which raised both scoring and the danger to pitchers and infielders. The "minus three" rule means a bat that is 33 inches long must weigh at least 30 ounces.

The names of bats follow a convention. A bat labeled "33/30" is 33 inches long and 30 ounces, so it is a "minus three." At youth levels the allowed difference between length and weight is larger, because younger players are smaller. If you are buying a bat for a young player, the league's own rules decide which bats are legal, and a coach or the league office can confirm that before you spend money. For softball, which has its own bats and balls, see our softball section.

The baseball: what the rulebook specifies

The rulebook describes the ball in one sentence. It is a sphere formed by yarn or similar material wound around a small core of cork, rubber or similar material, covered with two strips of white horsehide or cowhide stitched together tightly. It weighs not less than five and not more than five and a quarter ounces, and its circumference is not less than nine and not more than nine and a quarter inches.

In metric units that is roughly 142 to 149 grams and 23 to 23.5 centimeters around. The ball has red stitching, 108 double stitches in a standard baseball, which gives pitchers something to grip and gives the ball its familiar spin pattern. Modern major-league balls are covered in cowhide and are made by Rawlings, which has been the supplier since 1977, and the balls are assembled in Costa Rica.

The tolerance matters. A ball at the top of the legal range is about five percent heavier than one at the bottom. The rules specify ranges, not an exact value, because manufacturing is not perfectly uniform. The debate about whether the ball changed in the late 2010s, when home runs rose sharply, is a debate about exactly how the ball is made. A committee commissioned by the league concluded that changes in the ball's air resistance explained part of the increase, which is a reminder that a ball can meet the written specification and still behave differently.

Handling the ball: mud, humidors and foreign substances

A brand-new ball is slick. Before each major-league game, umpires rub the balls with a special mud, taken from a tributary of the Delaware River in New Jersey, to remove the shine and give pitchers a better grip. That practice has been used since the late 1930s and is one of the more unusual details in the equipment rules. The mud is not a rule in itself; it is a league procedure.

Balls are also stored in climate-controlled rooms, called humidors, at major-league ballparks. Colorado began using one in 2002 to keep the ball from drying out at altitude, and the league has required them in all parks since 2022. A drier ball is harder and tends to travel farther, so storage conditions can change how far a fly ball carries. Moisture matters on the field too; rain delays, suspended games and official games explains what happens when weather interrupts play.

Pitchers are not allowed to put a foreign substance on the ball or to scuff it. The ban on the spitball dates to 1920, with a small group of pitchers allowed to keep using it for the rest of their careers. For decades the rule was enforced loosely. In 2021 the league announced stricter enforcement, with umpires inspecting pitchers and an automatic suspension for violations, because sticky substances such as tacky pastes had been increasing spin and with it strikeouts. A pitcher may use the rosin bag on the mound to dry his hands, but he may not put rosin on the ball.

Gloves: size limits by position

Gloves are regulated more loosely than bats and balls, but the rulebook sets maximums that differ by position. As of the 2025 season, the main limits are these; check the current rulebook for exact measurements.

The differences make sense. A catcher receives pitches at 90 miles per hour, and a bigger mitt helps. A first baseman is the one fielder who is regularly asked to catch low or wide throws from teammates, so the rules allow a larger scoop. Pitchers and the other fielders get a standard glove, and it is the standard that most youth players buy.

Pitchers have one more rule: the glove may not be white or gray, and it may not be distracting in the umpire's judgment. The reason is that a pale glove can make the ball harder for the batter to pick up at release. Pitchers also may not attach foreign material to their gloves.

Why the limits exist

Each rule solves a specific problem.

1. Fairness. If one team could use a thicker bat or a livelier ball, the contest would be uneven. Standard dimensions make sure the game is decided by play.
2. Safety. A bat that sends the ball faster, or a pitcher's glove that hides the ball, makes the game more dangerous for fielders and batters. The BBCOR standard and the glove color rule are both safety measures.
3. Preserving the balance between hitting and pitching. The ball's specifications and the 2.61-inch barrel limit keep the sport's offense and defense in a stable relationship. When they drift, the league intervenes, as it did with sticky substances.
4. Continuity. A game that has been played for more than a century with the same basic equipment lets fans compare eras. Our guide to the unwritten rules of baseball covers the customs that grew up alongside the written ones.

Common questions

How long can a major-league bat be? No more than 42 inches, and it must be a single piece of wood with a barrel no thicker than 2.61 inches.

Is there a weight limit on a bat? Not in the professional rules. At the college and high school level, the weight can be no more than three ounces below the length in inches.

How much pine tar can a hitter use? Up to 18 inches from the end of the handle. Past that, the bat is illegal, but under the rulebook's current wording the usual consequence is that the bat is removed, not that the batter is called out after the fact.

How much does a baseball weigh? Between five and five and a quarter ounces, with a circumference between nine and nine and a quarter inches.

Why do pitchers wear dark gloves? The rulebook bans white and gray gloves because a light glove can make the ball harder to see.

Where to go next

For the broader rulebook, the rules and umpiring topic page collects our explainers, and the lineup card and substitutions piece shows how the rules govern who can be in the game at all. If you keep your own scorebook, our online scoresheet lets you practice.