What is double start in darts?

Double start, or double in, means you must hit a double or the bullseye before you can begin scoring in a leg. Darts thrown before that score nothing. The World Grand Prix is the only PDC major played this way; the leg is then ordinary 501 and still has to be finished on a double.

Which darts tournament is double start?

Only the World Grand Prix. It is played double-start and in sets, with every set a first to three legs.

Can you throw a nine-darter with a double start?

Yes, but only from three openings. Of the 3,944 nine-dart routes available from a standard start, 574 remain legal under double-start rules. Only the bullseye, double 20 and double 17 can begin one; from any other double a nine-dart finish is impossible.

What does double 20 leave you on in a double start leg?

461. The bullseye leaves 451 and double 17 leaves 467. Those three are the only openings from which a nine-dart leg is still possible; every other double makes ten darts the fastest available.

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Double start: the Grand Prix rule

Every other tournament lets you start scoring with the first dart. At the World Grand Prix you have to hit a double to open the leg as well as to close it, and until you do, nothing counts. It makes the Grand Prix play very differently from the rest of the year.

Checked 6 November 2026. The numbers below are worked out from every possible route, not quoted.

How it works

You start on 501, but your first scoring dart has to land in a double, or the bullseye.
Darts thrown before that score nothing. Miss all three and you are still on 501 with your opponent to throw.
Once you are in, the leg is ordinary 501: score down, and finish on a double as usual.
Everything else about the tournament is normal. It is played in sets rather than straight legs, and every set is first to three legs.

What each opening double leaves you

Hit the double you are aiming at and this is your score. Three of them, and only three, leave a number you could still finish in nine darts. Every other opening makes a ten-darter the best that is mathematically available.

Open on	Leaves	Fewest darts possible	Ways to do it
D1	499	10 darts	19,536
D2	497	10 darts	38,472
D3	495	10 darts	20,880
D4	493	10 darts	65,352
D5	491	10 darts	110,224
D6	489	10 darts	81,336
D7	487	10 darts	192,456
D8	485	10 darts	296,928
D9	483	10 darts	262,240
D10	481	10 darts	518,624
D11	479	10 darts	756,104
D12	477	10 darts	746,904
D13	475	10 darts	1,304,424
D14	473	10 darts	1,829,184
D15	471	10 darts	1,941,504
D16	469	10 darts	3,101,360
D17	467	9 darts	7
D18	465	10 darts	4,700,408
D19	463	10 darts	7,032,176
D20	461	9 darts	84
BULL	451	9 darts	483

Double 17 is the oddity. It leaves 467, which is finishable in nine, but only 7 ways out of the millions of ten-dart routes available from a worse opening. It is a needle that has to be threaded perfectly from the second dart onwards.

The nine-darter maths

This is what double start really costs. A nine-dart leg from a standard start can be thrown a lot of different ways. Under Grand Prix rules, almost all of them become illegal, because the first dart is no longer free to be a treble 20.

3,944 Nine-darters with a normal start

574 Still legal double-start

14.6% Of the routes survive

3 Opening doubles that can start one

Only the bullseye, double 20 and double 17 can begin a double-start nine-darter. Open on any of the other eighteen doubles and a nine-dart finish is not unlikely, it is impossible: there is no combination of eight further darts that gets you home.

Both figures count ordered routes by segment, so single 20 and double 10 count as different darts even though they score the same. On that convention a standard nine-darter has 3,944 routes, which is the long-published number, and is how we know the model is right. The working is in the open: every route is enumerated rather than looked up.

Why seeds go out

Averages collapse at the Grand Prix, and they collapse unevenly. A player who misses three darts at a double to start has thrown a scoreless visit, which no amount of scoring power makes up for. The format rewards whoever gets in first far more than it rewards a big average, so seeds lose more often here.

The three-dart average you see on screen at the Grand Prix is also not comparable to a normal tournament. Those missed opening darts are in the divisor.

Practising a double start

It asks for one double at the very start of a leg, before you have any rhythm, and most practice routines never work on that. The free darts scorer will score a 501 leg for you, the checkout chart covers every finish from 2 to 170, and the checkout trainer drills the doubles until they stop feeling cold.