How is a chess Elo rating change calculated?
The Elo rating system calculates the probability of winning based on the difference between both players' ratings: Ea = 1 / (1 + 10^((Rb - Ra) / 400)). When the game finishes, your actual score (1 for win, 0.5 for draw, 0 for loss) is compared against your expected score. The difference is multiplied by your K-factor to yield your rating change: ΔR = K × (Score - Ea).
What K-factor applies to my FIDE rating?
Under FIDE regulations: K=40 applies to players who are new to the rating list until they have completed events with at least 30 games and for players under age 18 (provided their rating remains under 2300); K=20 applies to most active adult tournament players rated under 2400; K=10 applies to elite players once their published rating reaches 2400.
What is a Tournament Performance Rating (TPR)?
A Tournament Performance Rating (TPR) measures how strong your play was in a specific event. It takes the average rating of all your opponents and adds a differential adjustment (dp) corresponding to your percentage score. For instance, scoring 70% against an opponent average of 1600 yields a TPR of approximately 1750.