The setup measurements for electronic soft-tip dartboards are slightly different from the distances used for bristle dartboards.
The height of the dartboard at the center of the Bull, or Bullseye, should be 5 feet, 8 inches. The throwing distance is 8 feet, as measured along the floor, from the plane of the face of the dart board.
Don’t measure from the wall, as that would offset the measurement by the thickness of the board.
The easiest way accurately measure to the throw line is to use the diagonal measurement. Mount the board first, and check that the 5’8″ height is correct. Then hold one end of a tape measure at the Bull, and bring the other end out and down to the floor, so that the diagonal distance is 9 feet, 9-1/2 inches.
The Throwing Line is often called the Toe Line. At home or in most bars, this will be a piece of tape on the floor.
Darters generally like to stand on the tape or line, so measure the throwing distance to edge closest to the dartboard. (In steel-point darts play, this throw line is generally referred to as the Oche’.
About that diagonal measurement: If you recall your elementary school geometry, the 9′ – 9.5″ measurement is the longest side of the right triangle formed by the dartboard’s height and throwing distance along the floor. If one intersection of 3 lines is a right angle, and you know 2 of the line lengths, then the 3rd side can be calculated:
Height to Bull: 5′-8″
Throwing distance: 8′
Diagonal Bull to Toe Line: 9′- 9 1/2″