Grade Impact
Pick two players (or type two dGrades) and see how each player’s rating would move under both outcomes. Uses the official WCF GC formula: Δ = modulator × class × P(loser wins).
How the math works
The WCF GC system uses a Bradley-Terry-Zermelo model. The probability that the lower-rated player wins:
P(loser wins) = 1 / (1 + 10^((DG_winner − DG_loser) / divisor))
The post-game rating change is computed independently per player using their own modulator:
Δ_player = modulator_player × class_factor × P(loser wins)
Per-player modulators: Standard (18.8) for most players, Mobile (23.2) for players whose grade is moving rapidly. The WCF system auto-detects mobile by comparing each player’s current dGrade against their adjusted performance grade over the last 30 games — if the gap exceeds 51 points, the system uses the higher modulator until the gap closes. When the two players have different modulators, the system is no longer zero-sum: the winner’s gain may not equal the loser’s loss.
Why an upset moves grades more: when a strong favourite wins, P(loser wins) is small, so the grade move is small. When the upset happens, P(loser wins) was large (close to 1), so the move is large.
Divisors: 500 for 13-point games, 450 for 19-point games. Score is not factored in — a 7-6 nail-biter and a 7-0 thrashing produce identical grade changes.
Class factor: 1.16 for the knockout phase of championship-level events (national, regional, international championships), 1.00 for everything else, 0.76 for B/C-level events and consolation brackets within bigger events. The naming refers to the WCF’s rating-class taxonomy, not to event entry restrictions.
Caveat — single-game projection: the displayed numbers represent the move from a single completed game in isolation. The real WCF system applies an “updating algorithm” where future games further adjust grades, and a player’s grade is a running estimate, not a one-shot calculation.