Double out, master out, single out
In 501 and 301 you count down from the starting score and have to hit exactly zero. The out rule decides which dart may finish the leg. In steel-tip darts the rule is double out: the last dart has to be a double. The bullseye counts as a double, since it is two times 25. The outer bull ring worth 25 doesn't finish.
With master out and double out, a score of 1 is also a bust, because 1 can't be finished with a double. Dropping below zero is a bust too; the score goes back to what it was before the turn.
How to read the chart
Each row lists a score and a route of at most three darts. T stands for triple, D for double, a number alone for the single segment, 25 for the outer bull ring and Bull for the bullseye worth 50. For 96, for example, T20 · D18 means triple 20 for 60, then double 18 for the remaining 36.
Many scores have more than one route. The chart lists the common one, which usually leads to the popular doubles 20, 16 or 18. Double 16 is a proven target because 32 halves four times: if you hit single 16 instead of D16, you are left on 16 and thus D8, then D4, D2 and D1.
The bogey numbers
Seven scores below 171 can't be finished with three darts: 169, 168, 166, 165, 163, 162 and 159. That is pure arithmetic. The highest two-dart totals are 120 (T20, T20), 117 (T20, T19) and 114 (two T19s, or T20 and T18), and the finishing dart is worth at most 50. With these seven numbers there is always a remainder that no double and no bull can close. If you land on one, use the next throw to leave yourself a finishable score.
Two darts, one dart
With only two darts left in a turn, the highest finish is 110 with T20 and Bull. With a single dart, only even scores up to 40 (double 1 to double 20) and 50 (Bull) work. For scores where the chart lists three darts, you therefore set up first with fewer darts: leave a score you can finish on your next turn.
The chart works for 501 and 301 alike, because from 170 down the route is the same. Cricket players don't need it; there the goal is closing 15 to 20 and the bull. The cricket rules are on the Ochely page.
