Backgammon Galaxy’s New Rating System

The last time we updated the Backgammon Galaxy rating formula was in 2023. Recently, we made a new update, and we wanted to briefly explain what changed and why.

There are two main reasons for this update:

First, we discovered a bug in the formula that affected matches where the two players were within 100 rating points of each other. In those cases, the system was using an incorrect expected win rate inside the rating calculation. We've now fixed that issue so the rating adjustments behave as intended.

Second, we’ve slightly improved the expected win rate model itself. The new version is a bit more sophisticated, which should make rating adjustments more accurate over time.
We’ve also increased the K-value slightly. In practice, this means ratings may move a bit more after each match. Sometimes that will work in your favor, sometimes not—but over the long run it helps ratings reflect current playing strength a bit faster.

One thing that hasn’t changed is the core Backgammon Galaxy concept: if you win both the match and the Error Rate battle, you still earn 50% more rating points. That remains a key part of how our rating system rewards strong technical play.

Feel free to use our tool below to find out how your rating will change based on opponent rating.

Thanks for playing, and as always we appreciate the feedback and passion from this community.

Best regards,
Marc Olsen
CEO, Backgammon Galaxy