A cricket field consists of a large grassy ground on which the game of cricket is played; this is ostensibly an oval though most cricket grounds would more accurately be described either as a convex set or as a convex polygon with an infinite number of sides. Cricket grounds can be almost perfectly circular, elongated ovals or entirely irregular shapes with little or no symmetry – but they will have entirely curved boundaries, almost without exception. There are no fixed dimensions for the field but its diameter usually varies between 450 feet (137 m) and 500 feet (150 m). Cricket is unusual among major sports (along with Golf, Australian rules football and baseball) in that there is no official rule for a fixed-shape ground for professional games. On most grounds, a rope demarcates the perimeter of the field and is known as the boundary. Within the boundary and generally as close to the centre as possible will be the square which is an area of carefully prepared grass upon which cricket pitches can be prepared and marked for matches.
The ICC Standard Playing Conditions define the minimum and maximum size of the playing surface for international matches. Law 19.1 of ICC Test match Playing Conditions states:
"The playing area shall be a minimum of 150 yards (137.16 metres) from boundary to boundary square of the pitch, with the shorter of the two square boundaries being a minimum 65 yards (59.43 metres). The straight boundary at both ends of the pitch shall be a minimum of 70 yards (64.00 metres), measured from the centre of the pitch to be used. In all cases the aim shall be to provide the largest playing area, subject to no boundary exceeding 90 yards (82.29 meters) from the centre of the pitch to be used. "
In addition, the conditions require a minimum three-yard gap between the "rope" and the surrounding fencing or advertising boards. This allow players to dive without risk of injury.
The conditions contain a grandfather clause, which exempts stadiums built before October 2007. However, most stadiums which regularly host international games easily meet the minimum dimensions.