501 / 301 Darts

• Count down from the start score to exactly zero. Three darts make a turn. Players take turns; the starter alternates each leg. Decide the first thrower with a bull-off: closest to the centre goes first.
• Single is face value, double is 2x, treble is 3x. Outer bull is 25, inner bull is 50 and counts as a double. There is no treble bull.
• Maximum turn is 180. The highest checkout is 170 (T20, T20, bull).
• A dart that bounces out or misses the board scores 0 and still counts as a dart. It is not thrown again.

• With double out, the dart that reaches zero must be a double (the bull counts). Master out: a double or a treble. Straight out: any dart.
• It is a bust if a turn goes below zero, leaves 1 (double or master out), or reaches zero without a valid finishing dart. The whole turn is void, your score goes back to what it was before the turn, and the darts you have not thrown are skipped.
• Once someone checks out, the remaining darts are not thrown.
• With double out, you can't finish 169, 168, 166, 165, 163, 162 or 159 in three darts, or anything over 170.
• No three darts can score 163, 166, 169, 172, 173, 175, 176, 178 or 179, or anything over 180.

• Straight in (usual): every dart scores. Double in: nothing scores until a double (or bull) lands, often used with 301. Master in: a double or treble opens. Darts before you are in score 0.
• Double out (PDC, WDF and most leagues), master out, or straight out (beginners and children: only going below zero busts).
• 50/50 bull: some pubs score the outer bull 50 too, with only the inner bull counting as a double.
• First to legs sets the match length. Sets are not scored here.
• Bounce-outs, a dart sticking in another dart and darts thrown out of turn are settled by your league or house rules. Enter what the dart scored, using Miss for no score.

Full notes, rule sets (PDC, WDF/BDO, leagues) and sources are in the rules document.