MLB Rules & Game Structure

The game of baseball is built on a set of rules that have been refined for over a century, but the game keeps evolving. The 2026 season introduced one of the most significant changes in recent history with the Automated Ball-Strike (ABS) Challenge System, giving players the ability to contest umpire calls on balls and strikes for the first time at the major league level.

Whether you are new to the sport, returning after time away, or managing a facility that hosts baseball at any level, this guide covers how MLB games work from start to finish. It breaks down the structure of a game, how scoring and outs work, the key rules that shape gameplay, and the latest rule changes for the 2026 season. For complete field measurements at every level of play, see our Baseball Field Dimensions Guide.

2026 MLB Rule Changes

The 2026 season brought several notable changes to Major League Baseball, headlined by the introduction of the ABS Challenge System.

The ABS Challenge System. For the first time in MLB history, players can challenge an umpire's ball or strike call using an automated system that tracks the exact location of each pitch relative to the batter's strike zone. Each team starts the game with two challenges. Only the batter, pitcher, or catcher can initiate a challenge, and it must happen within approximately two seconds of the call. A successful challenge (where the umpire's call is overturned) does not count against the team's total. An unsuccessful challenge (where the call is confirmed) costs the team one of its two challenges. If a game goes to extra innings and a team has no challenges remaining, it receives one additional challenge per extra inning. Managers are not permitted to call for challenges, and players cannot receive direction from the dugout before challenging. The system debuted after several years of testing in the minor leagues and represents the biggest on-field rule change since the pitch clock was introduced in 2023.

Base Coach Positioning. Starting in 2026, umpires are instructed to enforce the base coach box more strictly. First-base and third-base coaches must remain within the boundaries of their designated box while the pitcher is on the rubber. A first violation results in a warning, and subsequent violations can lead to ejection. The rule is a response to coaches ranging further from their boxes to get better angles for reading pitchers' grips and relaying signs.

Baserunner Contact Rule. A baserunner who intentionally initiates contact with a fielder to draw an obstruction call can now be ruled out at the umpire's discretion, with all other runners returning to their last occupied base.

How a Baseball Game Works

An MLB game is played between two teams of nine players each. The game is divided into innings, and each inning has two halves: the top half, where the visiting team bats, and the bottom half, where the home team bats. Each half-inning continues until the defensive team records three outs.

How many innings are in an MLB game? A regulation MLB game consists of nine innings. If the score is tied after nine innings, the game goes to extra innings (covered below). If the home team is leading after the top of the ninth inning, the bottom half is not played.

How many players are on a baseball team? Each MLB team carries a roster of 26 players during the regular season. Nine players take the field on defense at any given time: a pitcher, catcher, first baseman, second baseman, shortstop, third baseman, left fielder, center fielder, and right fielder. The designated hitter (DH) bats in place of the pitcher but does not play a defensive position. The DH rule is universal across both the American League and National League as of 2022.

The flow of play follows a consistent cycle. The pitcher throws the ball from a raised mound 60 feet 6 inches from home plate. The batter attempts to hit the ball into fair territory. Fielders try to record outs by catching fly balls, tagging runners, or throwing to a base ahead of the runner. When three outs are recorded, the half-inning ends and the teams switch between offense and defense.

For facilities that host baseball at any level, the pitcher's mound is one of the most weather-vulnerable areas on the diamond. Rain spot covers protect the mound and home plate area from washouts that can compromise playing conditions between innings or during rain delays.

Scoring

Runs are the only unit of scoring in baseball. A run is scored when a baserunner legally touches first base, second base, third base, and home plate in order. The team with more runs at the end of nine innings (or extra innings, if needed) wins the game.

Ways to reach base. A batter can reach base by getting a hit (a batted ball that lands in fair territory without being caught), drawing a walk (four balls, meaning four pitches outside the strike zone), being hit by a pitch, reaching on an error (a defensive mistake), or reaching on a fielder's choice (where the defense opts to retire a different runner).

Scoring plays. The most common ways runs are driven in include singles and doubles that advance runners, sacrifice flies that allow a runner to tag up and score from third base, and home runs that clear the outfield fence and score the batter plus all runners on base. A grand slam, which is a home run with the bases loaded, scores four runs on a single swing.

Outfield fences play a direct role in scoring. The distance from home plate to the fence varies by ballpark, typically ranging from 300 to 355 feet down the foul lines and 390 to 435 feet to center field. At stadiums with hard outfield walls, outfield wall padding reduces the severity of collisions when fielders chase fly balls to the warning track. For a full breakdown of outfield dimensions across the league, see our MLB Stadium Dimensions Guide.

Outs

Each half-inning continues until the defensive team records three outs. There are several ways to make an out:

Strikeout. A batter is out after accumulating three strikes. A strike is called when the batter swings and misses, when the batter does not swing at a pitch within the strike zone, or when the batter hits a foul ball (except on the third strike, where a foul ball does not count as a strikeout unless it is a foul bunt). The strike zone is defined as the area over home plate between the midpoint of the batter's torso and the top of the knees. With the 2026 ABS Challenge System, batters and pitchers can now challenge borderline ball-strike calls for the first time.

Fly out. A fielder catches a batted ball before it touches the ground.

Ground out. A fielder picks up a ground ball and throws it to a base ahead of the runner before the runner arrives.

Tag out. A fielder with the ball touches a runner who is not safely on a base.

Force out. A fielder with the ball touches a base before a runner who is forced to advance reaches that base.

Double play. Two outs are recorded on a single play, most commonly a ground ball to an infielder who throws to second base for one out, with the relay to first base completing the second out.

Key Baseball Rules Every Fan Should Know

Baseball has several rules that are unique to the sport and often confuse newer fans. Here are the ones that come up most often during a game.

The infield fly rule. When there are runners on first and second base (or bases loaded) with fewer than two outs, and the batter hits a high pop-up that an infielder can catch with ordinary effort, the umpire calls "infield fly" and the batter is automatically out, regardless of whether the ball is actually caught. The purpose of this rule is to prevent the defense from intentionally dropping the ball to turn a double or triple play on the baserunners, who would otherwise need to stay close to their bases on a fly ball. Runners can still advance at their own risk after the call.

The pitch clock. Introduced in 2023, the pitch clock requires pitchers to begin their delivery within a set time limit after receiving the ball. With bases empty, the pitcher has 15 seconds. With runners on base, the limit extends to 18 seconds. Batters must be in the box and "alert to the pitcher" with 8 seconds remaining on the clock. A violation by the pitcher results in an automatic ball; a violation by the batter results in an automatic strike. The pitch clock reduced average game times by roughly 30 minutes in its first season and remains one of the most impactful pace-of-play changes in the sport's history.

The balk. A balk is an illegal motion by the pitcher while one or more runners are on base. When a balk is called, all runners advance one base. Common balk situations include the pitcher starting a delivery and then stopping, faking a throw to first base from the stretch position, or failing to come to a complete stop in the set position before delivering. The balk rule exists to prevent pitchers from deceiving baserunners with deceptive motions.

Infielder positioning. As of 2023, MLB requires at least two infielders on each side of second base and all four infielders to have both feet on the infield dirt when the pitch is delivered. This rule effectively banned the extreme defensive shifts that had become common, where three or four infielders would position themselves on one side of the field against pull-heavy hitters.

Replay review. Managers can challenge certain on-field calls using instant replay. Each manager starts the game with one challenge and receives a second if the first challenge is successful. Reviewable plays include tag plays, force plays, fair-foul calls, home runs, and several other categories. Ball-strike calls were not reviewable until the introduction of the ABS Challenge System in 2026 (which operates separately from the manager's replay challenges).

Extra Innings

What is the MLB extra-inning rule? If the score is tied after nine innings, the game enters extra innings. Each extra inning follows the same format as a regular inning, with one exception: since 2020, each half-inning of extras begins with a runner placed on second base (the "ghost runner" or automatic runner). This runner is the player who was due to bat last in the previous inning's batting order.

The automatic runner rule was introduced during the shortened 2020 season and made permanent in 2023. Its purpose is to increase the likelihood of scoring in extra innings and prevent games from extending indefinitely. Before this rule, extra-inning games could stretch well beyond 12 or 13 innings, creating challenges for pitching staffs and facility operations.

For fields that host day-night doubleheaders or extra-inning games that extend past sunset, proper lighting is essential, and field protection becomes even more important. Extended games mean additional innings of wear on the mound, base paths, and batter's box. FieldSaver infield rain tarps can be deployed quickly between games of a doubleheader to protect the skinned infield from weather and reset the surface for the next game.

The MLB Season and Postseason

How many games are in an MLB season? Each MLB team plays 162 regular-season games, running from late March through late September. The schedule follows a balanced format introduced in 2023, where teams play 52 divisional games, 62 non-division league games, and 48 interleague games. This means every team in baseball plays every other team at least once during the season.

How many MLB teams are there? There are 30 MLB teams split between two leagues: the American League (AL) and the National League (NL). Each league has three divisions (East, Central, and West) with five teams in each division.

The postseason. The MLB postseason begins in October with the Wild Card Series, a best-of-three round. From there, the Division Series (best of five), League Championship Series (best of seven), and World Series (best of seven) determine the champion. Six teams from each league qualify for the postseason: three division winners and three wild card teams.

A 162-game season puts extraordinary wear on a baseball field. Fields that host professional or college-level baseball benefit from growth covers during the offseason to protect turf from frost damage and accelerate spring green-up, and backstop padding to protect players and fans throughout a long season of foul balls and wild pitches. Our stadium and field padding guide covers outfield wall padding, fence rail pads, dugout padding, and fence top protection to complete your field's safety layout.

Shop Baseball Field Equipment

How Long Are MLB Games?

How long are MLB games? Since the introduction of the pitch clock in 2023, the average MLB game runs approximately 2 hours and 36 minutes. Before the pitch clock, average game times had crept above 3 hours. The pitch clock, combined with limits on mound visits and restrictions on defensive shifts, brought average game length down by roughly 30 minutes.

Factors that extend game time include pitching changes, replay reviews, ABS challenges (new for 2026), rain delays, and high-scoring innings with many plate appearances. Postseason games tend to run longer due to additional commercial breaks and the higher stakes that lead to more pitching changes.

Rain delays are one of the most unpredictable factors in game length. When a delay hits, the grounds crew's ability to get the field game-ready quickly depends on the equipment they have on hand. A full infield rain tarp covering the entire skinned area is the standard at the professional and college levels, and tarp rollers allow a small crew to deploy and retract a full tarp in under 15 minutes.

What Does MLB Stand For

MLB stands for Major League Baseball, the highest level of professional baseball in the United States and Canada. The league was formed in 1903 when the American League and National League agreed to operate under a single governing body. Today, MLB oversees 30 teams across two leagues, sets the official rules of the game, and operates the Minor League Development System. The complete Official Baseball Rules, maintained by the Official Playing Rules Committee, are available as a PDF from MLB.

CoverSports manufactures field protection equipment for professional stadiums, college programs, and community ball fields. From batting cages and foul ball netting to outfield windscreens and dugout rail pads, every product is built in Philadelphia and backed by over 150 years of manufacturing experience. Get a Free Quote or call (800) 445-6680.

Shop Baseball Field Equipment

Frequently Asked Questions

How many innings are in a baseball game?

A regulation MLB game consists of nine innings. If the score is tied after nine, extra innings are played with an automatic runner on second base to start each half-inning.

How many players are on a baseball team?

MLB rosters carry 26 players during the regular season. Nine players take the field on defense, with a designated hitter batting in place of the pitcher.

How many players are on the field in baseball?

Nine defensive players are on the field at a time: the pitcher, catcher, four infielders (first baseman, second baseman, shortstop, third baseman), and three outfielders (left field, center field, right field).

What is the infield fly rule in baseball?

The infield fly rule applies with runners on first and second (or bases loaded) and fewer than two outs. When a batter hits a catchable pop-up to the infield, the batter is automatically called out to prevent the defense from intentionally dropping the ball to turn a double play.

How many games are in an MLB season?

Each team plays 162 regular-season games. The balanced schedule ensures every team faces all 29 other teams at least once during the season.

How many MLB teams are there?

There are 30 MLB teams, 15 in the American League and 15 in the National League. Each league is divided into three five-team divisions (East, Central, and West).

How long are MLB games?

The average MLB game runs about 2 hours and 36 minutes since the pitch clock was introduced in 2023. Before the clock, games averaged over 3 hours.

What does MLB stand for?

MLB stands for Major League Baseball, the top professional baseball league in North America. It was formed in 1903 and currently operates 30 teams across two leagues.

What is the MLB pitch clock rule?

Pitchers have 15 seconds to begin their delivery with bases empty and 18 seconds with runners on base. Batters must be ready with 8 seconds remaining. Violations result in automatic balls (pitcher) or strikes (batter).

What is the MLB extra inning rule?

Since 2023, each half-inning of extra innings begins with an automatic runner on second base. This "ghost runner" is the player who made the last out (or was due up last) in the previous inning.

What is the ABS Challenge System?

New for 2026, the Automated Ball-Strike Challenge System lets batters, pitchers, or catchers challenge umpire ball-strike calls. Each team gets two challenges per game, and successful challenges are retained. The system uses automated tracking to determine the precise location of each pitch.