Official FIDE Rating Change Calculator
Calculates official rating deltas per FIDE Handbook Section B.02. Formula:
ΔR = K × (Score - Expected_Score).
Single Game Calculation
How Does FIDE Calculate Chess Ratings?
1. Expected Score (\(W_e\)): Based on the rating difference between you and your opponent, FIDE's formula calculates your statistical probability of winning or drawing:
We = 1 / (1 + 10^((Opponent_Rating - Your_Rating) / 400)).
2. Rating Change (\(\Delta R\)): When you perform better than expected, you gain points; perform worse, and you lose points:
ΔR = K × (Score - We).
3. FIDE K-Factors:
• K = 40: For players under 18 with ratings below 2300, or players with fewer than 30 FIDE rated games.
• K = 20: For all players rated under 2400 (most club and tournament players).
• K = 10: For players once they cross 2400 FIDE classical rating.