Baseball Rules Explained
A complete beginner-friendly guide to understanding baseball rules, from the basics to the pitch clock, infield fly rule, and everything in between.
The Basics: Innings, Outs, and Runs
A baseball game is divided into nine innings. Each inning consists of two halves: the top half, in which the visiting team bats, and the bottom half, in which the home team bats. An inning ends when the defensive team records three outs. A run is scored when a player successfully advances around all four bases and touches home plate. The team that scores more runs over nine innings wins the game. If the game is tied after nine, it proceeds to extra innings with the new universal runner rule that places a runner on second base to start each extra inning, designed to speed up resolution.
Strikes, Balls, and the Strike Zone
Each at-bat begins with the count at 0 balls and 0 strikes. A strike is called when a pitch passes through the strike zone (roughly from the batter's knees to the midpoint of the torso, over home plate) without being swung at, when the batter swings and misses, or when the batter hits a foul ball (though a foul ball cannot be the third strike unless caught). A ball is any pitch outside the strike zone that the batter does not swing at. Four balls result in a walk (the batter advances to first base). Three strikes result in a strikeout.
Getting Batters and Runners Out
There are many ways to record an out in baseball. A strikeout occurs with three strikes. A ground out occurs when a fielder catches a batted ball on the ground and throws to first base before the batter arrives. A fly out occurs when a fielder catches a batted ball in the air before it touches the ground. A tag out occurs when a fielder with the ball tags a baserunner who is not standing on a base. A force out occurs when a runner must advance and a fielder with the ball touches the base to which the runner is forced. Double plays (two outs on one play) and triple plays (three outs) are also possible.
Pitching Rules
Starting pitchers typically face the opposing lineup multiple times before being replaced by relief pitchers. There is no strict limit on how many pitches a pitcher can throw, though teams manage workloads for health reasons. A pitcher must throw to each batter until the at-bat resolves — a pitcher cannot intentionally walk a runner in fewer than four pitches, though the automatic intentional walk (four pitched balls waived) is allowed. If a pitcher starts an at-bat, they must face that batter until the at-bat concludes or the pitcher is removed due to injury.
The Pitch Clock and Modern Rules
In 2023, MLB introduced a pitch clock to reduce game times. Pitchers now have 15 seconds to begin their pitching motion with the bases empty and 20 seconds with runners on base. The batter must be in the batter's box, attentive to the pitcher, with at least 8 seconds left on the clock. Violations result in automatic balls for pitching violations and automatic strikes for batter violations. Pitchers are also limited to two disengagements (pickoff attempts or step-offs) per plate appearance, with a third disengagement resulting in a balk unless the runner is put out.
Base Running Rules
Runners must touch each base in order — first, second, third, home — when running the bases. Runners can attempt to advance on any batted ball, passed ball, or wild pitch. They can also attempt to steal bases by running while the pitcher is delivering the ball to home plate. Runners are out if tagged when off base, forced out at the next base, or pass another runner on the bases. On a fly ball, runners must return to their original base (tag up) before attempting to advance after the catch.
The Designated Hitter Rule
Since 2022, all 30 MLB teams use the designated hitter (DH). The DH bats in place of the pitcher, who does not take a turn in the batting order. The DH can be changed mid-game, but if the DH becomes a fielder, the pitcher must then bat, and the team loses the DH for the rest of the game. The universal DH has fundamentally changed roster construction and strategic thinking, adding an additional lineup slot for pure offensive talent.
The Infield Fly Rule
The infield fly rule is one of baseball's more complex rules. It applies when there are runners on first and second, or bases loaded, with fewer than two outs. If a batter hits a fair popup that an infielder can catch with ordinary effort, the umpire calls the batter out immediately — regardless of whether the ball is actually caught. This prevents fielders from intentionally dropping easy pop-ups to set up double or triple plays. Once the infield fly is called, baserunners may advance at their own risk, but they are not required to advance.
Common Baseball Terms Glossary
A plate appearance that results in a hit, out, or error (walks and sacrifices do not count as at-bats).
Earned Run Average — the average number of earned runs a pitcher allows per nine innings.
On-Base Percentage — how often a batter reaches base via hit, walk, or hit by pitch.
Total bases divided by at-bats. Measures raw power output.
On-Base Plus Slugging — the sum of OBP and SLG, a quick measure of overall offensive value.
Wins Above Replacement — estimates how many wins a player adds versus a replacement-level player.
Walks plus Hits per Inning Pitched — measures how many baserunners a pitcher allows per inning.
Awarded to a relief pitcher who finishes a winning game under certain conditions, including protecting a lead of three runs or less.
Awarded to a relief pitcher who enters in a save situation and leaves the game without giving up the lead.
An illegal pitcher movement with runners on base, resulting in all runners advancing one base.
A pitch so errant that the catcher cannot control it, allowing baserunners to advance.
When a pitched ball strikes the batter, who is awarded first base.
Frequently Asked Questions
How many innings are in a baseball game?
A standard MLB game consists of 9 innings. Each inning has a top half (visiting team bats) and a bottom half (home team bats). If the game is tied after 9 innings, it continues into extra innings until one team leads at the end of a complete inning.
What is the infield fly rule in baseball?
The infield fly rule automatically calls a batter out when a fair pop-up can be caught by an infielder with ordinary effort and there are runners on first and second base (or bases loaded) with fewer than two outs. This prevents fielders from intentionally dropping the ball to get multiple outs on a double or triple play.
What is the pitch clock rule in MLB?
MLB introduced a pitch clock in 2023 to speed up the pace of play. Pitchers have 15 seconds to begin their delivery with no runners on base and 20 seconds with runners on base. Batters must be ready in the batter's box with 8 seconds remaining. Violations result in automatic balls (for pitchers) or automatic strikes (for batters).
What is a designated hitter in baseball?
The designated hitter (DH) is a player who bats in the lineup but does not play a defensive position in the field. The DH was adopted universally by both American League and National League teams in 2022, replacing the tradition of pitchers batting. The DH allows teams to keep elite hitters healthy by not requiring them to play the field.
How does scoring work in baseball?
A run is scored when a baserunner successfully advances around all four bases — first, second, third, and home plate — without being put out. Runs can score via hits, walks, hit-by-pitches, wild pitches, passed balls, sacrifices, or any other means of advancing bases. The team with more runs after 9 innings wins.