Baseball Field Dimensions: Diamond, Bases & Outfield

Baseball field size: the infield

The infield is a 90-foot square set on its corner. These field dimensions baseball players at the high school, college and professional levels all share:

The 90-foot measurement is to the outside corners of first and third base and to the center of second base, which is why careful layout uses a measuring tape anchored at the back point of home plate. The mound’s slope starts 6 inches in front of the rubber and drops 1 inch per foot for 6 feet toward home plate.

Infield arc, baselines and skinned areas

On most fields the grass edge of the infield, called the infield arc, is laid out as a radius of about 95 feet measured from the front center of the pitching rubber. Base cutouts around first, second and third are typically circles of roughly 13 to 18 feet in radius depending on the level. The skinned path between home and the mound is common at older parks and some youth fields.

On synthetic fields these shapes are inlaid in contrasting turf colors or left as clay. Either way, the curves need to be cut precisely. A crooked arc or misplaced cutout is obvious from the stands and hard to correct once the turf is glued.

Major league baseball field dimensions: the outfield

The outfield is where ballparks differ. Major League Baseball’s Official Baseball Rules call for at least 325 feet from home plate to the nearest fence along each foul line and at least 400 feet to center field for parks built after 1958, though some older parks are shorter in spots. Most fields have a warning track about 15 feet wide inside the fence so fielders can feel the wall coming.

Foul lines run straight from the back point of home plate past first and third base to the foul poles. They must be precisely aligned, since the foul territory and fence distances are measured from them.

Youth and other field sizes

Many complexes build a single synthetic infield with removable or portable bases and mounds so one diamond can serve several age groups. Softball uses its own layout; see softball field dimensions for those numbers.

Keeping a field to spec when it is built

Dimensions on paper only matter if the field is graded and laid out to match. Builders start by setting home plate and the backstop line, then shoot the foul lines and base positions with survey equipment. The infield is typically graded with a slight slope from the mound area outward for drainage, and the outfield is crowned or sloped toward drains.

On a synthetic field, the base under the turf has to be laser-graded so the ball rolls true, and inlaid lines and arcs are cut and seamed before infill. Multi-sport complexes often fit a baseball diamond alongside other layouts, like a artificial turf soccer field in the outfield, which takes careful planning of colors and markings.

If you are planning a new diamond or converting a grass field, work with installers who handle professional turf installation for athletic fields and can lay out every measurement on a diamond accurately.