Should I double?
A free tool · Last updated 28 October 2026
In a match, the score changes when a double is right and when you should take one. Enter the score and the cube, and this page gives the chances to win you need, the same way the app’s bots decide.
The answers at every score
With the cube in the middle and the usual gammons, before the Crawford game. In each square: the chances to win you need to double, then the least you need to take. Rows are your score, columns theirs.
| You \ them | 0 | 1 |
|---|---|---|
| 0 | 64% · 30% | 55% · 27% |
| 1 | 68% · 34% | 50% · 32% |
| You \ them | 0 | 1 | 2 | 3 |
|---|---|---|---|---|
| 0 | 66% · 27% | 66% · 30% | 62% · 24% | 60% · 24% |
| 1 | 64% · 27% | 64% · 31% | 60% · 27% | 52% · 21% |
| 2 | 70% · 29% | 69% · 33% | 64% · 30% | 55% · 27% |
| 3 | 73% · 29% | 76% · 36% | 68% · 34% | 50% · 32% |
The Crawford game has no doubling. In the games after it, the player behind should double at once; the leader then takes or passes by the score.
How it’s worked out
A match equity table gives, for every score, each player’s chances to win the match between two equal players. Passing a double gives away the cube’s points now; taking plays for twice as many. The least you need to take is where both leave you the same chances to win the match.
On top of that, the player who takes owns the cube and can double back later, which lets them take a little lighter, and the doubler gives that up. We count it with Rick Janowski’s live-cube model, worked out level by level from the table. It’s how the app’s bots decide when they play on the iPhone. With the cube in the middle at 5 points each, for example, the plain sum says take with 24%, and owning the cube brings that down to 20% when there are no gammons.
These are a guide for a typical position at that score, not a verdict on yours: the position itself, and how likely gammons really are, move the numbers. The app’s review judges each of your doubles and takes in its real position.
The match equity table
We use the Kazaross-XG2 table, made by Neil Kazaross from rollouts by eXtreme Gammon and used by default in GNU Backgammon. Its chances for matches up to 5 points, from 0 to 100:
| You need \ they need | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| 1 | 50.0 | 67.7 | 75.1 | 81.4 | 84.2 |
| 2 | 32.3 | 50.0 | 59.9 | 66.9 | 74.4 |
| 3 | 24.9 | 40.1 | 50.0 | 57.2 | 64.8 |
| 4 | 18.6 | 33.1 | 42.8 | 50.0 | 57.7 |
| 5 | 15.8 | 25.6 | 35.2 | 42.3 | 50.0 |
| You need | 2 | 3 | 4 | 5 |
|---|---|---|---|---|
| Your chances | 48.8 | 32.3 | 31.0 | 19.0 |
Questions
- What about single games for points?
- Without a match score, the cube follows the points alone: take with about 21% or more chances to win when gammons are rare, and double from about 68%. Gammons and the position move both.
- Why does the page ask about gammons?
- A gammon counts twice the cube, so at some scores it wins or loses the match on its own. The more gammons a position has, the more they move the numbers.
More free tools: the race and shot calculator and the dice checker.