What is the regulation diameter of a standard steel-tip dartboard?

The regulation diameter of a standard steel-tip dartboard is 451 millimetres.

This measurement refers to the playing surface of the conventional bristle dartboard used in organised steel-tip darts. The board is circular, divided into 20 numbered sectors, and includes the double ring, treble ring and two bull areas.

The diameter is often rounded informally to about 45 centimetres, which can create confusion when people compare it with the overall size of a board cabinet or surround. Those external fittings are not part of the regulated scoring surface.

Board dimensions are considered alongside other setup measurements, including the bullseye height and the throwing distance. Electronic soft-tip boards can use different dimensions and equipment standards.