Why 24/23 13/9
24/23 13/9 is the standard play: the small split makes your back checkers harder to attack and easier to anchor, and the checker on your 9-point is a builder for the 5-point and the bar point.
The top five plays, rolled out
| # | Play | Equity | Behind the best | Wins | Gammons won · lost | 3-ply (rank) |
|---|---|---|---|---|---|---|
| 1 | 24/23 13/9 | +0.005 ±0.014 | — | 49.8% | 14.8% · 14.2% | −0.003 (#1) |
| 2 | 13/8 | −0.036 ±0.015 | 0.041 | 49.1% | 14.0% · 14.8% | −0.033 (#4) |
| 3 | 13/9 6/5 | −0.039 ±0.015 | 0.044 | 49.7% | 14.4% · 15.7% | −0.017 (#2) |
| 4 | 24/23 24/20 | −0.061 ±0.013 | 0.066 | 48.7% | 13.0% · 14.2% | −0.032 (#3) |
| 5 | 24/20 6/5 | −0.062 ±0.013 | 0.067 | 49.0% | 13.0% · 14.9% | −0.051 (#5) |
Equity is the average result in points per game for the player on roll, with the cube in play: each play rolled out 1,296 times, ± one standard error. Gammons include backgammons.
The alternatives
Bringing one checker safely to the 8-point with 13/8 trails by 0.041, and the slot 13/9 6/5 by 0.044. Splitting both back checkers with 24/23 24/20 is weaker still.
All 14 legal plays, ranked at 3-ply
- 24/23 13/9 −0.003
- 13/9 6/5 −0.017
- 24/23 24/20 −0.032
- 13/8 −0.033
- 24/20 6/5 −0.051
- 13/9 8/7 −0.114
- 24/23 8/4 −0.128
- 24/20 8/7 −0.138
- 24/23 6/2 −0.140
- 8/4 6/5 −0.149
- 8/3 −0.175
- 6/5 6/2 −0.207
- 8/7 6/2 −0.247
- 8/7 8/4 −0.329
Questions about the 4-1 opening
What is the best opening move for 4-1 in backgammon?
24/23 13/9 (split and build). In GNU Backgammon rollouts of the top five plays it scores +0.005, 0.041 ahead of the next play, 13/8.
Is 13/8 a mistake with an opening 4-1?
A small one. It gives up 0.041 points per game on average compared with 24/23 13/9.
How was this 4-1 analysis made?
GNU Backgammon 1.07.001 ranked all 14 legal plays at 3-ply, then rolled out the best five, 1,296 games each, with the cube in play (money game, Jacoby off). GNU Backgammon 1.06.002, the version Boardgammon’s servers run, ranks the same five plays in the same order at 3-ply.
How these numbers were made
GNU Backgammon 1.07.001 ranked every legal play at 3-ply with the cube in play (money game, Jacoby off, no beavers), then rolled out the best five: 1,296 games each, with variance reduction and quasi-random dice. GNU Backgammon 1.06.002, the version Boardgammon’s servers run, ranks the same five plays in the same order at 3-ply. Evaluated on 2026-10-20. The same engine analyses every finished online game on Boardgammon: see how that compares. New to the numbers? Read what equity and a rollout are.
Terms on this page: Builder, Anchor, Slot, Blot. Next in the strategy guides: cube theory.