501 rules: how to play X01

The basics

Players take turns throwing a visit of three darts. The total of the visit comes off your score. The first player to reach exactly zero wins the leg.

• A dart scores its segment times its ring: a single 20 is 20, a double 20 is 40, a treble 20 is 60.
• The outer bull is 25 and the bullseye counts as double 25, so 50.
• The most you can score in one visit is 180: three treble 20s.

Starting scores

Any other start works the same way. A handicap gives players different starts, so a newer player might start on 401 against your 501.

Double-in, straight-in and master-in

The in rule decides how you start scoring:

• Straight in: every dart counts from the first throw.
• Double in: nothing counts until you hit a double. That double counts, and so does every dart after it.
• Master in: like double in, but a treble also opens your score.

Double-out, straight-out and master-out

The out rule decides how you can finish:

• Double out (the standard): your last dart must be a double, and the bullseye counts as a double. You can't finish on 1, because there's no double worth 1.
• Master out: your last dart must be a double or a treble.
• Straight out: any dart that takes you to exactly zero wins. Good for beginners.

The bust rule

If a dart would take you below zero, the visit is a bust: your score goes back to what it was before the visit and your turn ends. With double-out or master-out you also bust if you land on exactly 1, or reach zero with a dart that isn't a double (or a double or treble for master-out).

Checkouts worth knowing

• 170 is the highest checkout: treble 20, treble 20, bullseye.
• Under double-out, 159, 162, 163, 165, 166, 168 and 169 can't be finished in three darts. Players call them bogey numbers.
• Good leaves are even numbers that halve cleanly: 32 (double 16) and 40 (double 20) give you several tries at a double if you miss into the single.

The checkout chart lists a route for every finish from 170 down to 2.

Sets and legs explained

One game of 501 is a leg. A match is a race to win a number of legs: first to 3 is the same as best of 5. Longer matches are played in sets: legs make up a set, and sets make up the match, so a final might be first to 7 sets, each first to 3 legs.

• The throw alternates every leg, so each player starts every other leg. In sets, whoever didn't start the last set starts the next one.
• Bull for throw: to decide who starts the match, each player throws one dart at the bull, and the closest throws first.
• Doubles: two pairs share one score per side, and partners take turns at the board, so the order runs player one, opponent one, player two, opponent two.

Darts or totals

The Darts App scores X01 dart by dart, or by each visit's total, the way most league scorers do. Switch between them above the keypad; each player's choice is remembered on the device.

• Totals: type what the three darts made, or tap a common score. Totals no three darts can make are refused: anything over 180, and 179, 178, 176, 175, 173, 172, 169, 166 and 163.
• Busts: enter the score thrown, or tap Bust. The bust rule applies as usual.
• Checkouts: when a total finishes the leg, say how many darts it took (if it could have been fewer than three) and how many were at a double. That keeps your checkout percentage and leg lengths honest.

How averages work

The three-dart average is the points you've scored divided by the darts thrown, times three: the average visit. The first-nine average uses only your first three visits of each leg, before checkouts get in the way. Checkout percentage is your checkouts divided by your darts at a finish: every dart you throw while one dart could win the leg (on 40, a dart at double 20; on 50, a dart at the bull). Darts thrown on a score no single dart can finish, bogey numbers included, never count. The Darts App works all three out from every leg you play against other people; solo legs stay out of your stats, and so do legs against a bot unless you choose to count them in Settings.