Every player starts with a capital of 501 points. The player throws a round of three darts (or less) and the score is added up. The result is subtracted from the player's capital, the aim being to reach exactly zero before the other player (without going past this figure). In order to reach zero, the player must throw the last dart of the leg into a "double" ring or the double centre (the term double out from the name of the game). If the player goes past zero, the whole of the round in hand is nullified. For example, a player with a capital of 24 must throw a dart into the "double 12" to finish the leg. If the player goes past zero, he is said to be "busted" and his capital of 24 points remains unchanged. It is no longer possible to win the leg by reaching 1.

A match is played over two or three winning legs, or even more for finals. In addition to the players, there is also a scorer for the game (who deals with counting up the legs).

A game of 501 ends after a minimum of 3 rounds (a total of 9 darts) and for this reason it is known as nine-darter. For example, a game may unfold as follows:

• ·first round: 3 triple twenties
• ·second round: 3 triple twenties
• third round: triple twenty, triple nineteen, double twelve

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