What are the dimensions of official dartboards?

Although the Darts Regulation Authority does not cite a board's dimensions in its rule book, the Darting website describes the standard board as being 18 inches in diameter. The official board must have 20 segments and a bull's eye in the center.

In competition, the center of the board is 5 feet, 8 inches off the ground, and players stand at least 7 feet, 9.25 inches from the board. A raised line called an "oche" indicates the closest the players may stand to the board. There should be an additional 2 feet of mat behind the player. The dart board is hung with the black "20" segment at the top, and should be well illuminated, according to the official rules.