Work out how many rating points you gain or lose for a game or a whole tournament, using the FIDE Elo formula — plus your expected score and performance rating.
Rating change = K × (actual score − expected score). The expected score is 1 / (1 + 10^((opponent rating − your rating) / 400)). A win scores 1, a draw ½ and a loss 0.
FIDE uses K = 40 for new players until they have 30 rated games and for juniors under 18 rated below 2300, K = 20 for players rated below 2400, and K = 10 once a player has reached 2400.
Your performance rating is the rating your results “performed at” in an event. A common estimate is the average opponent rating plus 400 × (wins − losses) ÷ games.
Because you were expected to win. The bigger the rating gap, the higher your expected score — so a win earns little and a loss costs a lot.
Play rated games on ChessStride, then train the exact positions you lose points in.