Darts Checkout Calculator

The structure of 501 darts

The standard professional darts game is 501. Each player starts at 501 points and counts down to exactly zero. The first to hit zero (with the final dart landing in a double or the bullseye) wins the leg.

If you go below zero (a “bust”), the throw doesn’t count and you return to your previous score. Going to exactly 1 is also a bust, because you cannot finish on a single. The final dart must land in a double or the bull (which counts as a double 25).

This rule structure creates the famous “checkout” problem: from any given score, what’s the optimal 1, 2, or 3-dart sequence to finish on a double?

The dartboard layout

Understanding the board is essential. A standard dartboard:

• 20 numbered segments (1-20 around the board)
• Each segment has a single (most of the area), a double (outer thin ring), and a treble/triple (inner thin ring)
• Bullseye: 50 (inner bull) + 25 (outer bull)
• Treble 20 (T20) = 60 points (highest single-dart score)
• Three darts maximum per turn = 180 max (T20, T20, T20)

The board layout was designed by Brian Gamlin in 1896 to punish inaccuracy. Numbers are arranged so that missing a high segment lands you in a low one: 20 is flanked by 1 and 5; 19 by 7 and 3.

The highest possible checkout: 170

The maximum 3-dart finish is 170:

• T20 (60) + T20 (60) + Bull (50) = 170

Higher scores require 4+ darts. Anyone shouting “one hundred and EIGHTY!” has just thrown a maximum visit (T20, T20, T20). Anyone hitting a 170 finish is performing the highest possible finishing combination.

Impossible checkouts, and the arithmetic behind them

Seven scores between 2 and 170 cannot be finished in three darts. They are called “bogey numbers”: 169, 168, 166, 165, 163, 162 and 159.

The reason is easier than it looks. Two darts can total anything up to 120, but not everything: nine totals in that range simply cannot be made, because no pair of segments adds up to them.

103, 106, 109, 112, 113, 115, 116, 118, 119

Take a bogey score, subtract the biggest legal finisher, and what you are left with is always one of those nine.

Anything smaller than the bull as a last dart leaves an even bigger remainder, so it fails too. That is the whole proof.

Land on one of these with three darts in hand and you cannot win this visit, so the job changes: throw to leave yourself a good number for the next one. From 169 the usual line is T20, T20, S17, which scores 137 and leaves 32 for the double you actually want.

The professional’s favorite finish: 32

Professional players prefer to finish on D16 (32):

• If you hit D16: you’ve won
• If you miss into single 16: you have 16 left, which is D8
• If you miss D8: you have 8 left, which is D4
• If you miss D4: you have 4 left, which is D2
• If you miss D2: you have 2 left, which is D1

The 16-8-4-2-1 “power of 2” path means each miss leaves a cleanly halved double. This is why pros set up to leave 32.

By contrast, miss a D17 and you have 17 left (need T7+D? or another path requiring 2 darts). The clean halving doesn’t work.

Other preferred finishing doubles

Avoid finishing on doubles with odd “ladders” (D11, D13, D17). A miss leaves an awkward remainder.

The classic finishing routes

The most-used checkouts among professional players:

Checkout percentage, the key pro stat

Professional darts players’ “checkout percentage” tracks the success rate of attempted finishing visits. Top players:

A 40% checkout percentage means hitting roughly 2 out of 5 attempted finishes. The remaining 60% leave the opponent an opportunity.

The 9-darter, darts’ perfect game

A “9-dart finish” is the minimum-darts checkout from 501, the darts equivalent of a bowler’s perfect game. The mathematical structure:

Standard 9-darter route:

• T20, T20, T20 = 180 (321 left)
• T20, T20, T20 = 180 (141 left)
• T20, T19, D12 = 141 (zero, checkout)

Or:

• T20, T20, T20 = 180 (321 left)
• T20, T20, T20 = 180 (141 left)
• T17, T18, Bull = 141 (zero)

The first 9-darter on UK television: Paul Lim, 1990 World Championship. Since then, 9-darters have become much more common as players have improved. Phil Taylor hit 11 televised 9-darters. Michael van Gerwen has hit several including back-to-back.

The cricket variant

In addition to 501, “Cricket” is a popular American darts game where players score by hitting numbers 15-20 and the bull three times each. Different strategy, different math. Many calculators specifically handle 501 because it’s the standard professional format.

Tactical considerations

Setup darts: when you can’t finish in 3 darts (169, 168, 166 and the rest), you “set up” by leaving a workable number for the next visit. The target is almost always 32, sometimes 40. Two worked routes:

• From 169: T20, T20, S17 scores 137 and leaves 32
• From 99: T19, S10 scores 67 and leaves 32

Opponent watching: in tournament play, watch your opponent’s average. If they’re averaging 100/visit, you have approximately 5 visits before they finish 501. Plan accordingly.

Stress mathematics: under pressure, players often “freeze” on calculating finishes. Knowing common checkouts (170, 160, 100, 81, 60, 40, 32, 24) reduces cognitive load.

Practice routines

Top players practice checkouts intentionally:

• Around the clock: hit each double 1-20 in order with 3 darts
• 170 challenge: hit T20, T20, Bull as many times as possible in 10 minutes
• Setup practice: from various scores, practice leaving 32 or 40
• Treble 20 grouping: 100 darts at T20 to track accuracy

Phil Taylor reportedly practiced 6-8 hours per day at his peak. Most professional players practice 2-4 hours daily.