Double out, double in, master out: the x01 variants explained

October 27, 2026

x01 is simple on paper: start from a score and bring it down to exactly zero. But the name covers several ways of playing, depending on how you're allowed to start and how you have to finish. Here are the variants you'll come across, and which one suits you.

What they all have in common

Whatever the variant, each player throws 3 darts per visit, and the total is taken off their score. The first player to reach exactly zero wins the leg. The variants only change two things: the dart that opens your scoring (the "in") and the dart that closes it (the "out").

Finishing rules

Straight out

Any dart can finish: a single, a double, a treble, the bull. You just need to land on zero. It's the most forgiving version, ideal when you're starting out or for a quick game with friends.

Double out

The competition rule. Your last dart has to land in a double (the outer ring) or the inner bull worth 50, which counts as a double. Finishing means hitting a narrow target, and that's the whole point: a player can lead the entire leg and still lose it on the doubles. To know what to aim for, keep the checkout chart handy.

Master out

A middle ground: you can finish on a double or a treble (and the 50 bull). There are more ways out than in double out, but you still have to hit a ring. A good stepping stone before moving up to double out.

Starting rules

Straight in

The usual case: every dart counts from your very first visit.

Double in

Nothing counts until you've hit a double. Darts thrown before that aren't taken off your score, while the dart that hits the double does count. It adds real tension at the start: a player who misses the opening double can watch their opponent disappear into the distance. Double in, played with double out, is the format of the PDC World Grand Prix.

Master in

Same idea, but a double or a treble is enough to get you going. More forgiving than double in.

Busts, variant by variant

A bust is a cancelled visit: your score goes back to what it was at the start of the turn, and the darts already thrown in that turn don't count. You bust when you:

go below zero, in every variant;
reach zero without meeting the finishing rule (a single in double out, for example);
are left on 1 in double out or master out, since no double or treble is worth 1.

In straight out, being left on 1 is no problem: a single 1 finishes it.

101, 301, 501, 701, 1001: which starting score?

101: an express game, a few visits and it's done. Perfect for practising your finishes.
301: a short leg, often paired with double in.
501: the reference format, the one you see in tournaments and on TV. A top player can finish it in 9 darts, the fewest possible.
701 and 1001: longer legs, handy for team play where each team shares one score.

The higher the starting score, the more the game rewards consistent scoring. The lower it is, the more it all comes down to finishing.

Legs and sets

A leg is a single game: start from the starting score and count down to zero. A match is played over a "best of" number of legs: in best of 5, the first to 3 legs wins.

In the big tournaments, legs are grouped into sets: you need to win a certain number of legs to take a set, then a certain number of sets to take the match. At the PDC World Championship, a set goes to the first player to win 3 legs. At home, best of 3 or best of 5 legs is plenty.

Which variant for your level

Just starting out: 301 or 501 straight out. You learn to score without spending half an hour stuck on a double.
Hitting the rings fairly often: move up to master out. You get used to aiming at a specific area to finish, with a bit more margin.
Playing at a club or looking to improve: 501 double out, the standard format. It's the one that gets you ready for real matches.
Fancy a challenge: add double in, or try 101 double in, double out to work on both ends of the leg.

With Throw

In Throw, x01 runs from 101 to 1001, with straight in, double in or master in, and double out, master out or straight out, over legs from best of 1 to best of 11. The 50 bull counts as a double throughout. Stand your phone beside the board and it scores every dart and applies the variant you picked, busts included, while a checkout route helps you close the leg out. To try it, install the app: it's free and it works offline.