Baseball is played between two teams of nine players who take turns batting and fielding. A standard professional game has nine innings, and each inning is split into two halves: the visiting team bats in the top half and the home team bats in the bottom half. The batting team scores runs when its players advance around first, second, and third base and touch home plate. The fielding team tries to record three outs to end each half-inning. Pitchers try to throw strikes past batters, batters try to hit the ball into play, and the team with more runs after nine innings wins. If the score is tied, the game continues into extra innings.
Rulebook note: this is a simplified overview. Rules differ between MLB, NCAA, NFHS high school baseball, and youth organizations such as Little League, and professional rules are updated periodically. For exact wording and current changes, consult the official rulebook for your level.
The basics at a glance
| Rule | Detail |
|---|---|
| Players | Nine fielders per team: pitcher, catcher, four infielders, and three outfielders |
| Innings | Nine in professional and college baseball; seven in high school and many youth leagues |
| Outs | Three outs end each half-inning |
| Strikes | Three strikes is a strikeout; foul balls count as strikes until the batter has two strikes, except for foul bunts, which can be a third strike |
| Balls | Four balls is a walk, and the batter goes to first base |
| Scoring | A run scores when a runner touches home after touching each base in order |
| Fair and foul | Determined by the foul lines and where the ball is touched, passes, or settles |
| Ties | Extra innings are played until a winner is decided, with tiebreaker rules at many levels |
The field
A baseball field has a diamond-shaped infield with four bases 90 feet apart at the professional, college, and high school levels, and shorter distances in many youth divisions. The pitcher throws from a raised mound, 60 feet 6 inches from home plate at those levels. Foul lines run from home plate past first and third base to the outfield fences. Any ball that lands in fair territory, or passes first or third base in fair territory, is generally a fair ball.
How a half-inning works
- The batter comes to the plate. Batters hit in a fixed order called the lineup or batting order.
- The pitcher throws. Each pitch is a ball, a strike, a foul, or a ball put in play.
- The batter reaches base or is out. Batters reach base by hits, walks, being hit by a pitch, fielding errors, and other situations.
- Runners advance. Runners move around the bases on hits, walks, steals, and other plays.
- Runs score. Each runner who touches home plate legally scores a run.
- Three outs end the half-inning. The teams then switch between batting and fielding.
The strike zone
The strike zone is the area over home plate that a pitch must pass through to be called a strike if the batter does not swing. In general terms, it extends from around the batter’s knees up to a point between the shoulders and the top of the pants, based on the batter’s normal stance, and its width is the 17-inch width of home plate. Any part of the ball passing through any part of the zone counts. Exact definitions vary slightly by rulebook, and in practice the plate umpire judges each pitch. A pitch the batter swings at and misses is a strike regardless of location.
Ways to get out
- Strikeout. The batter gets three strikes, subject to the dropped third strike rule at some levels.
- Fly out. A batted ball caught in the air by a fielder before it touches the ground.
- Force out. A fielder with the ball touches a base that a runner is forced to advance to.
- Tag out. A fielder tags a runner who is not touching a base.
- Interference and other violations. Runners or batters can be called out for interfering with fielders, running out of the baseline to avoid a tag, and other infractions.
Ways to reach base
- Hit. A single, double, triple, or home run.
- Walk. Four balls.
- Hit by pitch. A pitch that touches the batter, in most cases.
- Error. A fielding mistake that allows the batter to reach.
- Fielder’s choice. The defense chooses to put out another runner instead of the batter.
- Dropped third strike. At many levels, if the catcher does not catch strike three cleanly and first base is open or there are two outs, the batter may run to first.
- Catcher’s interference. The catcher interferes with the batter’s swing.
Substitutions and the designated hitter
Teams can substitute players during the game, but in traditional baseball rules, a player who leaves the game cannot return. Some youth and amateur leagues allow re-entry or continuous batting orders. The designated hitter, or DH, bats in place of the pitcher. MLB adopted a universal designated hitter for both leagues starting in 2022, and many college and high school leagues also use a DH, though the specific rules differ.
Recent MLB rule changes
Major League Baseball introduced several changes in recent seasons to speed up games and increase action. They include a pitch clock that limits the time between pitches, limits on pickoff attempts and other disengagements from the rubber, restrictions on extreme defensive shifts that require two infielders on each side of second base, and larger bases. MLB also uses an automatic runner on second base to begin each extra inning in the regular season. These rules apply to MLB and some affiliated leagues but not necessarily to amateur baseball, and details can change from year to year.
Key rules that confuse new fans
| Rule | Simple explanation |
|---|---|
| Infield fly rule | With runners on first and second, or bases loaded, and fewer than two outs, the batter is automatically out on a catchable infield pop-up |
| Balk | An illegal pitcher motion with runners on base; each runner advances one base |
| Tag up | On a caught fly ball, runners must retouch their base before advancing |
| Ground rule double | A fair ball that bounces over or through the outfield fence; batter and runners advance two bases |
| Obstruction | A fielder without the ball impedes a runner, who may be awarded a base |
Common mistakes new fans and players make
- Thinking foul balls never count. Fouls count as strikes until two strikes.
- Running through second or third base. Only first base can be overrun without risking a tag.
- Forgetting to tag up. Runners who leave early on a caught fly ball can be called out on appeal.
- Assuming all levels use the same rules. Innings, distances, pitch limits, and substitution rules vary.
- Missing a base. Runners must touch every base in order, or they can be called out on appeal.
Frequently asked questions
How many innings are in a baseball game?
Professional and college games are nine innings. High school and many youth games are seven innings or fewer. Tied games go to extra innings.
How many outs are in an inning?
Each team gets three outs per half-inning, so an inning has six outs in total.
What happens if a baseball game is tied?
The game continues into extra innings until one team leads after a complete extra inning, or the home team takes the lead in its half of the inning. Some levels use tiebreaker rules, such as starting extra innings with a runner on second base.
