Which parts of the board count as a double?
The narrow outer scoring ring is the double ring. Its segments score twice the printed number: D10 is 20, D16 is 32 and D20 is 40. The small center bull scores 50 and counts as double 25 for finishing. The outer bull scores 25 and is not a double.
The triple ring does not count as a double even when its points equal your remaining total. With 18 left, triple 6 scores 18 but cannot be a double-out finish. Double 9 can. You need the correct segment as well as the correct arithmetic.
| Remaining | A valid one-dart finish | Why |
|---|---|---|
| 20 | D10 | 2 × 10 = 20 |
| 32 | D16 | 2 × 16 = 32 |
| 40 | D20 | 2 × 20 = 40 |
| 50 | Inner bull | Counts as double 25 |
The three ways to bust
A bust ends the current turn. None of that turn’s points are kept: return to the score you had before its first dart. Under double-out, a turn busts if you score more than you have left, leave exactly 1, or reach zero without a double.
Leaving 1 is a bust because the smallest double scores 2. There is no possible single-dart double finish from 1. You cannot keep that 1 for a later turn.
| Start this turn on | What happens | Result |
|---|---|---|
| 20 | Hit single 20 | Zero without a double: bust; return to 20 |
| 20 | Hit single 19 | Leaves 1: bust; return to 20 |
| 20 | Hit triple 20 | Scores too much: bust; return to 20 |
| 20 | Hit double 10 | Exact double finish: win |
A bust resets the whole turn
Suppose you begin on 40. Your first dart hits single 20, leaving 20. Your second hits single 19, leaving 1. That second dart busts the turn, so you go back to 40. You do not stay on 20, and you do not throw a third dart to repair the bust.
Now take a different turn from 40: single 20, miss, single 5. That scores 25 and leaves 15. Nothing has busted, so 15 carries into your next turn. An odd remaining score is allowed; 1 is the special case that cannot be finished.
An odd score needs a setup dart
Every double has an even value. If you have 15 left, a single 3 leaves 12, then D6 can finish. If you have 19 left, single 3 leaves 16 for D8. These are examples of valid routes, not the only targets available.
Look at the new remaining score after every hit. From 32, aiming for D16 but hitting single 16 leaves 16, so D8 becomes a possible finish. Missing the scoring area leaves the score unchanged. If you still have a dart in that turn, you can try again.
Using double-out in DartMate
The Double out switch is available when setting up either 301 or 501. Use it when your group wants a double finish. Switch it off for an open finish, where a single, double, triple or bull may take you to exactly zero. In that mode, leaving 1 is allowed, but scoring beyond zero still busts.
Throw at your real dartboard, then mark the actual segments on your iPhone. DartMate calculates the points from your taps. The Plus bust guide can dim regions that would be invalid under the active rule; it is not a camera detector or a route-planning coach.
If a result looks unexpected, check the finishing option and which ring you entered. A single 20 and D10 both score 20, yet only one is a valid double-out finish from 20.
Can the bullseye finish a double-out game?
Yes. The inner bull scores 50 and counts as double 25, so it finishes when you have exactly 50 remaining. The outer bull scores 25 and is not a double.
Must all three darts be doubles?
No. Only the dart that takes your score to zero must be a double. Earlier darts in a valid turn can score singles, triples or bulls. Stop when you make the finish.
Sources & scope
The examples apply the standard double-out and bust rules. DartMate’s open-finish option is described separately. Follow the organizer’s rules in organized play.