The official distance from the front of the dart board to the toe line is 7 feet, 9.25 inches, per rules from the Darts Regulation Authority and World Darts Federation. The National Darts Association stipulates the foul line is 8 feet away from the front of a dart board.
Before World War II, the standard distance away from a dart board was 9 feet. In 1977, the WDF set the line for official tournaments slightly further away, and this remains the current approved distance in 2014.
The toe line is known as the hockey in Great Britain, probably because the brewery Hockey & Sons held popular dart competitions. The throw line at Hockey & Sons was three crates away from the dart board, and each crate was 3 feet long, giving the original hockey line distance of 9 feet.