Performance Rating
What PR measures, the formula behind it, which decisions count (and which XG calls "obvious"), the skill bands and their colors, and how PR pools across matches.
Performance Rating (PR) is a single number that summarizes how close your choices were to the engine's best across an analyzed match. Lower is better — a PR of 0 would mean you played the top move on every decision. It's the same metric eXtreme Gammon reports, computed the same way, so your BackgammonDB numbers line up with XG's.
PR sits under Match Statistics, which covers the error bands and luck it's built alongside.
The formula
PR = (total equity lost ÷ number of decisions) × 500
Equity lost is the sum of how much each move gave up against the best available move (a move that matched the best gives up nothing). Decisions is the count of non-obvious choices you faced. Multiplying by 500 scales it into the familiar PR range.
For 1-point matches the result is multiplied by 1.5, matching XG's convention (single-game variance is compressed, so the rating is scaled up to stay comparable). Multi-point matches and money sessions use the plain formula.
BackgammonDB takes each move's equity loss straight from the analyzed file rather than recomputing it, so its PR matches the source program's to the digit.
Which decisions count
Not every move is a real decision. "Obvious" moves are excluded from the decision count so they don't dilute the score. BackgammonDB follows XG's definition rather than guessing:
- Forced moves — the dice leave only one legal play.
- Moves XG flagged as not counting — XG's analysis writes an irrelevant flag on a move whose choice didn't matter, and BackgammonDB honors it directly. (BackgammonDB doesn't apply an equity-spread cutoff of its own; it trusts the file's flag.)
- Obvious cube decisions — an optional double where doubling changes nothing; an obvious no-double; a position too good to double; and a double that's very negative either way. These follow XG's cube-obviousness rules.
Two kinds of decision are never treated as obvious:
- Any double you actually made.
- Any take/pass decision.
Equity lost on resignations (both a bad resign and a bad accept of one) still counts toward the total, but resigns don't add to the decision count — exactly matching XG's "include resign errors" mode.
No upper cap
BackgammonDB applies no ceiling to PR — a thoroughly rough match scores however high the formula puts it, well above 30 if earned. This is a deliberate difference from XG, whose interface displays anything over ~100 as a flat "100.00". The formula itself has no cap in either program; only XG's display clamps it.
Skill bands
PR maps to a named skill level (mirroring the XG manual), each shown in its own color wherever the PR number appears:
| PR range | Level |
|---|---|
| 0.0 – 2.5 | World Champ |
| 2.5 – 5.0 | World Class |
| 5.0 – 7.5 | Expert |
| 7.5 – 12.5 | Advanced |
| 12.5 – 17.5 | Intermediate |
| 17.5 – 22.5 | Casual Player |
| 22.5 – 30.0 | Beginner |
| 30.0 + | Distracted |
The same colors paint the band segments behind the library's PR range sliders.
PR across many matches
The library headline pools PR across all your matches by summing equity lost over all decisions — not by averaging each match's PR. That keeps a 3-decision game from counting as much as a 200-decision one; the pooled figure is the decision-weighted average of your matches.
Find your weakest decisions on the positions browser, where every blunder is tagged by position type and phase. The error bands and luck that sit alongside PR are on Match Statistics.