Baseball Basics: How Many Innings Are There in Baseball?

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We explain how many innings there are in baseball, how long a game can last, and whether there are any exceptions.

innings in baseball
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What is an Inning in Baseball?

An inning in baseball is made up of six outs: three by the home team and three by the visiting team. Once those six outs are recorded, an inning is completed.

Both teams take a turn batting and on defense.

How Many Innings are There in Baseball?

In Major League Baseball (MLB) and all of its minor leagues, as well as college baseball and international competition, there are nine innings in a regulation baseball game.

In high school baseball, there are generally seven innings in a regulation baseball game.

There are exceptions typical at every level, including the extra innings needed when the score is tied at the end of a regulation game.

Fewer than the regulation number of innings can be played in international baseball, college baseball and high school baseball when a “mercy rule” is enforced.

For example, the World Baseball Classic rules governing international competition state a team winning by 10 or more runs after seven (or eight) innings are played will be declared the winner.

High school baseball “mercy rule” guidelines, too, are in place and vary from state to state.

  • Professional baseball – 9 innings
  • College baseball – 9 innings
  • High school baseball – 7 innings

For all professional, college and high school baseball games, extra innings will be played until a winner is determined.

A few states have high school games that are played with a six-inning maximum.

Why is Baseball Nine Innings?

Before you learn how to bet on baseball, you need to understand some of the absolute basics.

Baseball is played in nine innings because the rules of the game dictate its length.

When the sport began, the game was played until one team scored 21 “aces” – a term that soon became “runs.” As the years rolled by, the time it took to reach 21 grew longer.

In 1856, baseball officials decided to use nine innings – and nine players per side.

One of baseball’s founding fathers, Alexander Cartwright, led the Knickerbocker Club and had a strong voice in rules changes.

MLB Historian John Thorn on the Nine Innings Rule

“In an 1856 Knickerbocker meeting, (two members) backed a motion to permit nonmembers to take part in intramural games if fewer than eighteen … were present … Duncan F. Curry countermoved that if fourteen … were available, the game should admit no outsiders and be played shorthanded, as had been their practice since 1845.

“Sensing that an official ruling was necessary as more and more baseball teams were formed, the Knickerbockers decided to form a committee in 1856 to tackle the issue. The desire for more competitive defense won out, and nine innings — and nine men — became the standard for good.”

What Happens After Nine Innings?

After nine innings are played and one team has scored more runs than the other, the game is declared complete.

If the teams are tied after nine innings, the game goes into extra innings and is played until one team scores more runs than the other in a subsequent inning.

You can find betting markets related to innings at most online sports betting sites so it’s worth knowing all the rules before you place any wagers.

How Long is a Baseball Game?

Baseball games were played in a little more than 2 ½ hours for much of the 1900s, but more frequent pitching changes, timeouts and expanded time taken by the batters stretched the average time for a game to more than three hours in 2016.

When games reached an average time of 3:10 in 2021, baseball officials began instituting changes such as the timeouts allotted for a batter and a requirement that relief pitchers must face at least three batters.

A device called “PitchCom” that speeds communication between catcher and pitcher helped bring the average game time to 3:04 in 2022.

The “pitch clock,” a limit on the amount of time a pitcher can take between pitches, was implemented for the 2023 season and game times were reduced by another 24 minutes, down to 2 hours 40 minutes.

During the 2023 season, it became clear that the changes were working spectacularly. Only nine times last season did a game reach 3 ½ hours – quite a difference from 2021 when there were a staggering 390 such games.

What is the Longest Baseball Game?

Theoretically, a baseball game can last forever but the longest game in MLB history was a 25-inning contest in 1984 between the Chicago White Sox and Milwaukee Brewers that lasted more than eight hours.

The Brooklyn Robins (later the Dodgers) and Boston Braves played to a 1-1 tie over 26 innings in 1920, but that one lasted only 3:50.

In the minor leagues, a 1981 game between the Rochester Red Wings and Pawtucket Red Sox lasted 33 innings and more than eight hours.

Jay Dieffenbach
Sports Betting Expert
Jay Dieffenbach
Sports Betting Expert

Jay is a Sports Betting Writer at Techopedia.com, and has been working in US sports for more than 20 years. He's worked for Daily Racing Form, the Arizona Republic, The Athletic and FanDuel among other sports and gambling positions.