Player Performance Rating Calculator
Calculate a player's performance rating based on their results against opponents of known ratings. Uses the FIDE performance rating formula: Performance Rating = Average Opponent Rating + Rating Difference based on score percentage.
Formula
Performance Rating = Average Opponent Rating + dp
Where dp is the rating difference corresponding to the player's score percentage, looked up from the FIDE dp table (based on the logistic/Elo probability function).
Score Percentage (p) = Total Score / Number of Games
The dp table maps score percentages to rating differences using the inverse of the Elo expected score formula:
E = 1 / (1 + 10^(−dp/400)) → dp = 400 × log₁₀(p / (1 − p))
Rating Change = K × (Actual Score − Expected Score)
Where Expected Score = Σ 1 / (1 + 10^((Opponent Rating − Your Rating) / 400))
Assumptions & References
- Uses the official FIDE dp (rating difference) table as published in the FIDE Handbook, Section B02.
- Performance rating is most meaningful for tournament sections with 5 or more games.
- Score percentages of 0% or 100% use the boundary values of ±800 dp (FIDE convention).
- Rating differences are capped at ±400 points per game when calculating expected scores (FIDE rule).
- K-factor of 40 applies to new players (fewer than 30 rated games); K=20 for players rated below 2400; K=10 for players who have ever reached 2400 or above.
- This calculator follows FIDE Elo rating system methodology (Arpad Elo, 1978).
- Reference: FIDE Rating Regulations effective from 1 July 2017, FIDE Handbook.
- Valid opponent rating range: 0–3500. Results must be 1 (win), 0.5 (draw), or 0 (loss).