Dartboards, according to the Darts Regulation Authority, should be measured such that the bullseye is 5 feet 8 inches tall. You should also stand approximately 7 feet 9.25 inches away.  The easiest way to make sure you are installing your dartboard cabinet correctly is to measure from the bottom of the cabinet to the bullseye and subtract that amount from the 5 feet 8 inches mark listed above. Then you can simply measure whatever that remaining amount is and place the bottom of your cabinet at that point on the wall.