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MLB Rules and Regulations

MLB LawsThe actual Major League Baseball rulebook is over 184 pages long. Over the sport’s long history, spanning from the nineteenth century until today, there have been countless changes and additions made to the game.

It would all be far too much material to share with you here, and quite a boring read to boot. Instead, we’re going to break down the most important rules and explain how the game is played so that you have a solid understanding without getting bogged down by all the details.

An exciting aspect of Major League Baseball rules is that there are actually two sets of them. The MLB is split into two leagues, the American League and the National League. For most of history, these were actually two separate legal entities, although this is no longer the case. Regardless, to this day, they play by slightly different sets of rules, which we will cover later.


It’s also important to note that every season, new rules are added, while old rules are changed. Heading into the 2018 season, there were numerous alterations. Now, there are limits on the number of warm-up pitches allowed, a set amount of mound visits per game, and the length of time between doubleheaders is now standardized.

So, as you can see, a ton of thought goes into this game and making it the best possible experience for the players, owners, and fans.

How the Game Is Played

Baseball is a classic bat-and-ball game played between two teams of nine or ten players, depending on whether a designated hitter is being utilized or not. The game is divided into nine innings, each of which consists of a top and bottom half. The top of the inning sees the away team batting, while the home team pitches and plays defense in the field. The bottom half of the inning is the exact opposite.

The object of the game is for the pitcher to throw a ball past home plate and into the catcher’s (who sits behind home plate and receives the ball each pitch) mitt while the batter tries to hit the ball with their bat. Anytime the batter swings and misses the baseball, hits into foul territory, or fails to swing at a pitch within the umpire’s “strike zone,” they are given a “strike.”


Balls pitched out of the strike zone are ruled “balls.” If a hitter gets three strikes, they’re out, whereas should they get four balls, they automatically freely advance to first base.

The defense is attempting to secure three outs to end the inning. Until three outs are recorded, the offense continues cycling through the nine-man batting order in an attempt to score as many runs as possible.

The offense is trying to hit the ball into the field, at which point they run to occupy any one of the three bases, not including home plate. Runners progress in a counter-clockwise direction, and if they are tagged with the ball or beaten to the plate by the ball, they are out.

When the ball is hit, it must stay “fair” within the two foul lines on either side of the field in order for the runners to advance. While the ball is live, the offense must touch first, second, third, and home plate in succession to score. However, if the ball is hit in the air and caught by one of the fielders, the batter is out. At the end of the nine innings, whichever team has scored the most runs wins the game.


PitchingThe pitcher takes their position on the “rubber,” which is a rubber slab positioned precisely sixty feet and six inches from home plate. This pitcher’s slab is in the middle of a mound of raised dirt that measures eighteen feet in diameter and is elevated no more than ten inches above the field.

From atop the hill, the pitcher must always keep one foot in contact with the rubber once they begin their pitch and can only move off of it once the ball has left their hand.

Easily the most critical player in the sport, the pitcher is one of the two players involved in every defensive play, with the catcher being the other. And though they both participate in each offering, the pitcher has a much larger impact on the outcome of the contest.

They use a variety of strategies to get the opposing team’s lineup out, including causing a pop fly which is caught for an out, force outs when a runner has no open base behind them and the ball is caught by the fielder standing on the next base, tag outs when the runner is touched with the ball while not standing on a plate, and strikeouts when the hitter receives three strikes.


When a pitcher is struggling or needs a break to speak with the catcher and/or manager, they are given a brief period of time for a mound visit. Each team is allowed only six mound visits now, with a seventh provided if the game goes to extra innings.

Sometimes a mound visit concludes with the manager making a pitching change, at which point a fresh pitcher comes to the mound from the bullpen, and the previous pitcher is retired for the day. Once a pitcher is subbed out, they may not re-enter the game.

If a pitcher hits a batter with the ball, they automatically proceed to first base freely. A slugger may also advance to first without connecting with the ball if they are walked, or a balk occurs. A walk is when the pitcher throws four “balls,” which means four pitches were thrown outside of the strike zone and the hitter did not swing.

A balk is when one or more runners are on base, and the pitcher makes an illegal move, most commonly pretending to throw a pitch without actually doing so. This action is penalized by moving all base runners up one base.


BattingThe lineup is a list of all nine players from the field in the order that they will come to the plate. Once the order is set for the game, it cannot be changed except for when a substitution is made, and even then, the positions stay the same; only the subbed player changes.

The offensive players try to score runs by both getting hits and advancing around the bases or by hitting the ball over the outfield wall, which is a home run. In the case of a home run, all base runners and the batter automatically score.

Any given at-bat does not begin until the batter is standing inside one of the two batter’s boxes, which are located on either side of home plate. Left-handed hitters typically position themselves in the left box, while right-handed players do the opposite. Once they’re set, the umpire restarts the action, and the pitcher serves up their throw.

To put the ball in play, a batter must make contact with it using their bat and have the projectile travel either through the air or by rolling on the ground into the field of play. This area includes everything inside the two baselines, which extend from home plate towards third and first base and all the way to the outfield wall. Everything that lands outside of these lines, closer to the stands, is foul.


Anytime the ball is put into play as fair, it’s the batter’s job to advance to first, at least, before the ball is thrown to the defensive player standing on the base. If the baserunner has no open bases behind them, and the ball reaches an infielder standing on the plate ahead of them, they are forced out.

If there is an open option for them, but the runner still proceeds forward, even if the ball reaches the defender first, they must physically tag the runner with the ball to get them out. If they slide into the plate and make contact with it before being tagged, the baserunner is called “safe.”

The Stadium and the Diamond

Pitcher’s Mound

The pitcher’s mound is located directly in the center of the baseball diamond. The raised dirt area can only be ten inches tall or shorter and houses the rubber slab on which the pitcher must stand when delivering their pitch. The distance from the rubber to home plate is sixty feet and six inches.


There are a total of four stations, including the first, second, and third bases, as well as the home plate. The distance between succeeding bases is ninety feet. The distance from home plate to second base is 127 feet and 3 3/8 inches. The distance from first to third is the same.

There is an umpire overlooking each base. Their job is to call runners “out” or “safe” on any given play involving baserunners. The offense travels counter-clockwise to round the base path and must touch each bag before advancing to the next one.

Foul Pole and Baseline

The first baseline extends from the right side of the plate through first base and straight back to the right outfield wall. There, the line continues vertically into the air in the form of the foul pole. These act as a boundary for the field of play. Any ball hit to the right of the first baseline and pole is considered a foul. On the other hand, any shot played to the left of the first baseline is fair.

Similarly, the third baseline extends from the left side of home plate to third base and then on to the left field wall. On this side of the field, any ball hit to the left of the boundary is foul, while baseballs knocked to the right are fair.

The foul poles are particularly useful for fly balls that are hit down the baseline, as they help determine on which side of the line the projectile traveled through the air.

Outfield Dimensions

Major League Baseball outfields are where things really get interesting. While most sports have consistent, uniform fields of play, baseball allows for some creativity in this department. Each team designs their outfield as they see fit, and no two parks are the same. They have different outfield wall heights, distances from the infield, and dimensions in general. For a time, Minute Maid Park in Houston even had a small hill in centerfield.

While teams have a decent amount of autonomy when it comes to ballpark design, there are still some fundamental specifications that must be followed.

For Example

The outfield wall must be at least 250 feet from home plate at the foul poles and is actually recommended to be at least 320 feet. The distance from home plate to the center field must be at least 400 feet.

Beyond these basic criteria, teams are free to do as they please. They are given the option to choose the height, shape, composition, and in many cases, the distance from home plate that they prefer. This results in some stadiums benefiting hitting, while others are known as pitcher’s parks. Depending on the shape of the outfield, some fields help right- or left-handed batters more.

The extreme variation from park to park is the reason park factors play such a central role in baseball handicapping. The actual environment becomes a significant variable in the overall equation. One of the reasons home field advantage exists in the MLB is because teams build rosters best suited for their home ballpark.

American League vs. National League

Now that we’ve covered the basic rules of the game, we should point out that the MLB is actually two separate leagues with slightly different bylaws. Technically, the two leagues stopped operating independently in 2000, when the legal entities were combined into one organization. Regardless, in the spirit of tradition, the two associations continue to each bring a unique approach to the game.

AL – Designated Hitter

In the American League, pitchers are not included in the batting order. Instead, they are replaced by a designated hitter. This player does not go into the field during the defensive half of the inning, and instead exclusively takes at-bats.

This allows teams to insert another slugger into the lineup in place of the traditionally-weak pitcher’s spot while also allowing the AL pitchers to focus all of their attention on their job on the mount.

NL – Pitchers Hit

In the National League, there’s no such thing as a designated hitter. The pitchers are part of the lineup and have to take at-bats. Most pitchers struggle at the plate on offense, which adds an extra layer of strategy to National League games.

Managers must decide when to pinch-hit for their pitcher late in the game, which then makes them ineligible to return to the mound. This added wrinkle means the coaching staff must plan their late-game substitutions to maximize the output they get from the hill, while also not giving up crucial at-bats late in the game when a pinch-hitter would have a higher chance of getting on base.

NL – Double Switch

Another aspect of the game that’s unique to the National League is the double switch. This is a form of substitution made by the defense and can be a bit complicated. This is how it works:

  • The pitcher (Player 1), who is due up to bat soon on offense, is subbed out and replaced by a position player (Player 2) with stronger batting skills, who takes their place in the lineup.
  • A position player (Player 3), who is batting after Player 1, is also subbed out and replaced by a pitcher (Player 4), who receives their spot in the batting order.
  • Now, despite who they were subbed out for, Player 4 takes over on the mound, and Player 2 takes over for Player 3 in the field.

So, what this maneuver does is allow a team to change the order of their lineup legally. When timed correctly, a team can significantly improve the strength of the batting order due up to bat in the next inning. They are taking a weak spot in the lineup that the pitcher was occupying and replacing it with a fielder of their choice and delaying how soon the new pitcher will have to hit. These are usually used late in close games when every at-bat counts.

Interleague Play/World Series

During the regular season, a portion of each team’s schedule is dedicated to interleague play, which is when American League and National League teams face off against each other. For most of baseball’s history, the only interleague games took place in the World Series, but since 1997, Major League Baseball has made these games a fixture of the regular season as well.


When teams from the two leagues compete, home field determines the set of rules under which the game will be played. In American League stadiums, both sides use a designated hitter, while in National League ballparks, all pitchers hit.

This holds true for the World Series as well. As you can imagine, this presents a significant advantage to the team with home-field advantage in the playoffs.

The Wrap-Up

While baseball may seem like a relatively straightforward game, it actually has a long, complicated rulebook. Every year, a committee proposes and makes changes to address current concerns. It’s a constant effort to make the game competitive, fair, and enjoyable to watch. Sometimes these goals must be sacrificed for each other in an attempt to find the perfect balance.

If you’d like to continue reading up on the rules of Major League Baseball, they can be found in PDF form here. Everything is measured and accounted for, from the uniforms to the bats to the balls and the bases. This ensures a fair contest that’s enjoyable to both watch and play.

The two leagues may vary on their use of a designated hitter, but the majority of the rules stay consistent between them

The slight difference adds an interesting wrinkle to interleague play and the World Series, while not being so significant as to impact the competition disproportionately.

And should things get out of balance, the rules committee will be there to vote on changes the very next offseason. That’s how the sport stays great – with constant evolution and adaptation to an ever-changing sports marketplace.