By the numbers
Updated
Independent desk. Figures are traced to named sources and corrections are logged — see the editorial policy.
Bases 90 feet apart, a mound 60 feet 6 inches from the plate, and a minimum fence distance that is a rule, not a recommendation.
Baseball is famous for letting every ballpark have a different outfield, and almost nothing else on the field is allowed to change. The infield is a fixed geometry, set in the nineteenth century and unchanged since.
The infield
- Bases: 90 feet apart, measured from the point of home plate to the back of first base, and from base to base.
- Pitcher's rubber: 60 feet 6 inches from the back point of home plate.
- Mound: the top of the mound may be no more than 10 inches above the level of home plate.
- Home plate: 17 inches wide.
- Bases: 15 inches square for first, second and third.
The 90-foot figure is the reason a close play at first is decided by an inch: the distance is short enough that a good runner and a good throw reach it within a fraction of a second of each other.
The outfield
The rules require that a new ballpark has a minimum of 325 feet from home plate to the nearest fence along the foul lines, and recommend 400 feet to centre field. Existing parks built before the rule are exempt, which is why a few of them are shorter. Everything beyond those minimums is up to the architect, which is why each park has its own shape.
Equipment limits
A bat can be no more than 2.61 inches in diameter at its thickest point and no more than 42 inches long. The ball is between 9 and 9¼ inches around and weighs 5 to 5¼ ounces. A pitcher has to keep one foot on the rubber while delivering a pitch from the windup or the set position.
Why the numbers still hold
Some changes have been proposed over the years, including a lower mound after 1968, the year the mound was reduced from 15 inches to the present 10 after a season in which pitchers dominated. The base distance has never changed, and no one in the game has proposed changing it.