Formula
Ten-pin scoring, the way World Bowling and the USBC count a game. A strike takes the next two rolls. A spare takes the next one. An open frame is the sum of its two rolls. The tenth frame may include fill balls, and those fill balls are part of the tenth frame’s score, not a new frame.
strike = 10 + next two rolls
spare = 10 + next roll
open = first + second
perfect game = 12 strikes = 300
Worked examples
A strike, then 7 and 3, then 9 and 0. The strike is 10 + 7 + 3 = 20. The spare is 10 + 9 = 19, so the running total is 39. The open frame adds 9. Running total 48.
Ten spares of 5, fill ball 5. Each frame is 15. The game is 150. Ten open frames of 9 and 0 are 90. Twelve strikes are 300.
Reference
Three finished games, used as the checks for this scorer.
| Game | Score |
|---|---|
| 12 strikes | 300 |
| Ten 5-spare frames, fill ball 5 | 150 |
| Ten frames of 9 and 0 | 90 |
| Strike, then 7/3, then 9/0, game unfinished | 48 through frame 3 |
Questions
How does a bowling score calculator count a strike?
A strike is 10 plus the next two rolls. Those two rolls also score in their own frames. Twelve strikes is 300. The tenth frame is where the two extra rolls are actually thrown.
How does a spare score?
A spare is 10 plus the next roll only. Ten frames of 5 and a spare, with a fill ball of 5, is 150. An open frame is just the two rolls added together. Ten frames of 9 and 0 is 90.
What is a bowling handicap calculator, then?
Handicap is not the game score. A league posts a basis and a percent, often something like (220 − average) × 80%, and that number is added to the scratch score. The basis and the percent belong to the league. This page scores the game. It does not invent a handicap.
Why is the tenth frame different?
If the first ball is a strike, or the first two make a spare, you get a fill ball. An open tenth frame does not. After a strike, the next two balls are scored as a frame: they cannot add past 10 unless the second of them is also a strike.
Sources
- World Bowling / USBC ten-pin scoring. Strike adds the next two rolls. Spare adds the next roll. The tenth frame awards fill balls after a mark.