Baseball basics
Baseball rules: innings, runs and outs explained
A practical guide to the basic flow of baseball: how teams alternate between batting and fielding, how an inning ends, how runs score and how a standard regulation game is structured.
How an inning works
An inning is split into two half-innings. The visiting team bats in the top half and the home team bats in the bottom half, while the other team fields. A half-inning ends when the fielding team records three outs, after which the teams switch roles.
What an out means
An out retires a batter or runner. Common outs include strikeouts, caught fly balls, force outs and tag outs. Once three outs are recorded in a half-inning, that side’s turn at bat is over; some plays can record two or even three outs at once.
How runs are scored
A run scores when a runner legally advances around first, second and third base and touches home plate, subject to the rules governing the play. The team with more valid runs at the end of the game wins.
How long a baseball game lasts
Under MLB’s professional rules, a regulation game normally consists of nine innings, with the bottom of the ninth omitted when the home team is already ahead. A tie after nine innings goes to extra innings. Other leagues, age groups and competitions can use different game lengths or tie procedures, so the competition rules control.