What a three-dart average measures
A three-dart average expresses scoring as points per three darts thrown. Add the points that actually reduced the score, divide by the number of darts recorded, then multiply by three. A completed 501 leg in 21 darts gives 501 ÷ 21 × 3 = 71.57. It is a description of that performance, not a prediction of who will win the next match.
A worked unfinished-leg example
Suppose your first four visits are 60, 45, 100 and 26. You have scored 231 points with 12 darts, leaving 270 from 501. The average is 231 ÷ 12 × 3 = 57.75. Do not divide by the number of visits and multiply by three again: that counts the three-dart grouping twice.
Checkout darts change the calculation
If you finish a leg with the first dart of the final visit, that visit used one dart, not three. Finishing 501 in 19 darts gives 79.11; recording two unnecessary darts would incorrectly turn it into a 21-dart leg and 71.57. When the scorer asks for checkout darts used, include any misses before the successful double, but do not count darts you never threw.
What happens on a bust?
A bust cancels the scoring from the whole visit. If you begin on 32, hit single 20 and then single 13, the visit scores zero and the remaining total returns to 32. Darts already thrown still belong in the dart count. The digital result depends on the darts recorded by the scorer; historical totals alone cannot reconstruct a missing dart count.
Combine legs using points and darts
Do not simply average the displayed averages of two different-length legs. If one leg takes 21 darts and another takes 30, the combined average is 1,002 ÷ 51 × 3 = 58.94. The arithmetic mean of the two leg averages would give each leg equal weight despite the different dart counts.
First-nine average answers a different question
First-nine scoring focuses on the opening phase of a leg, before most finishing attempts. For opening visits of 60, 100 and 45, the first-nine average is 205 ÷ 9 × 3 = 68.33. Compare it with the full-leg average to see how much the later phase changes the number. A difference does not prove poor doubles: setup visits and fewer scoring opportunities can also affect it.
Use averages alongside results
A player can lose with a higher average because the opponent takes the important double first. Read legs won, high finishes, scoring bands and recent form alongside the average. Compare several sessions played under similar conditions instead of treating a personal-best leg as a normal level.
Use the average calculator or read real recorded match summaries.