Why 24/23 13/8
24/23 13/8 brings a checker safely down to your 8-point and makes a small split. 13/8 6/5 brings the same checker down but slots the 5-point with the 1 instead.
The top five plays, rolled out
| # | Play | Equity | Behind the best | Wins | Gammons won · lost | 3-ply (rank) |
|---|---|---|---|---|---|---|
| 1 | 24/23 13/8 | −0.014 ±0.014 | — | 50.0% | 13.9% · 13.5% | +0.013 (#1) |
| 2 | 13/8 6/5 | −0.019 ±0.013 | 0.005 ≈ | 49.6% | 14.2% · 14.2% | −0.014 (#2) |
| 3 | 24/18 | −0.048 ±0.013 | 0.034 | 49.4% | 12.6% · 14.4% | −0.028 (#3) |
| 4 | 13/7 | −0.099 ±0.015 | 0.085 | 47.8% | 13.9% · 15.2% | −0.074 (#4) |
| 5 | 24/23 8/3 | −0.196 ±0.013 | 0.182 | 45.7% | 12.9% · 17.4% | −0.163 (#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. ≈ marks a play behind the best by less than twice the larger standard error, inside the margin of error.
The alternatives
The two finish 0.005 apart in the rollouts, too close to call, so the choice is a matter of style. Running 24/18 trails by 0.034; 13/7 and 24/23 8/3 are clear errors.
All 8 legal plays, ranked at 3-ply
- 24/23 13/8 +0.013
- 13/8 6/5 −0.014
- 24/18 −0.028
- 13/7 −0.074
- 24/23 8/3 −0.163
- 8/3 6/5 −0.190
- 8/2 −0.202
- 8/7 8/3 −0.373
Questions about the 5-1 opening
What is the best opening move for 5-1 in backgammon?
24/23 13/8 and 13/8 6/5 are effectively tied. In GNU Backgammon rollouts of the top five plays, 24/23 13/8 scores −0.014 and 13/8 6/5 −0.019, a gap inside the margin of error.
Is 13/8 6/5 a mistake with an opening 5-1?
No. It finishes 0.005 behind 24/23 13/8 in GNU Backgammon’s rollouts, inside their margin of error, so the two plays are effectively equal.
How was this 5-1 analysis made?
GNU Backgammon 1.07.001 ranked all 8 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: Slot, Builder, Blot, Golden point. Next in the strategy guides: cube theory.