Dartboard Dimensions — Official Sizes & Segment Measurements | Oche

A tournament-legal clock dartboard is built to millimetre tolerances, and every one of those numbers is fixed by the sport’s governing bodies. Whether you’re buying a board or checking the one you have, these are the measurements that make it regulation.

The board

The overall diameter is 451 mm. The part that actually scores — the playing area — spans 340 mm, measured across the outer edges of the double ring. Everything outside the double ring (the number band) scores nothing.

Rings and beds

Both the double and treble rings are 8 mm wide, measured inside the bounding wires. The centre of the treble wire sits 107 mm from the centre of the bull, and the centre of the double wire sits 170 mm out. The 20 thin wedges (segments) each subtend 18° around the board.

The bull

At the centre, the inner bull — worth 50 — is 12.7 mm in diameter, ringed by the outer bull (25), which is 31.8 mm across.

Number layout

The numbers run, clockwise from the top: 20, 1, 18, 4, 13, 6, 10, 15, 2, 17, 3, 19, 7, 16, 8, 11, 14, 9, 12, 5. The sequence is not random — high-value beds sit beside low ones (20 between 1 and 5) so a slightly stray dart is punished, which is exactly why accuracy is rewarded.