Chess Rating Calculator
Work out what a whole tournament did to your rating. Enter your wins, draws and losses against the average rating of the field and the calculator returns the rating change and your performance rating.
Calculating a whole event
Rating a tournament is the single game formula applied once per round and added up. Against a field with a known average rating you can shortcut it: compute the expected score for one game, multiply by the number of games, and compare with what you actually scored.
change = K x (actual score - expected score per game x games)
This is exact when every opponent is at the average and very close in practice when the field is reasonably tight. If your opponents ranged from 1200 to 2100, calculate the rounds individually with the single game calculator instead, because the curve is not linear.
Performance rating
Performance rating answers a different question from rating change. It ignores your current rating entirely and asks: what rating would a player need, for this score against this field to be exactly what the formula expected of them?
FIDE computes it by converting your percentage score into a rating difference from the average opponent, using a published conversion table, then adding that difference to the average. Score 50 percent and your performance equals the field average. Score 75 percent and it is about 193 points above. FIDE leaves the value undefined for a perfect or a zero score, because the formula would require an infinite rating, and this calculator says so rather than inventing a number.
Performance rating is the better measure of how you played in one event. Rating change is the better measure of what the event did to your official number, because it is damped by K on purpose.
Choosing the right K
Use 40 if you have played fewer than 30 rated games, 20 if you are an established player under 2400, and 10 at 2400 and above. National federations sometimes use different values, and online sites use Glicko-style systems instead of plain Elo, so treat an online result as an approximation.
What a good event does not tell you
A strong performance rating is worth enjoying, and it is still only a result. It does not say whether you were well prepared or lucky, whether your endgames held or your opponents collapsed, or which habit will cost you the next event.
For that you need the games. Chess DNA analyses them with Stockfish at depth 18 and sorts every error into nine weakness themes, so the review of an event ends with something specific to work on rather than a number to feel good or bad about.
Frequently Asked Questions
How do I calculate my chess rating change for a tournament?
Take your expected score per game from the rating gap to the average opponent, multiply it by the number of games, subtract that from what you actually scored, and multiply by your K-factor. The calculator above does this for you.
What is a performance rating in chess?
It is the rating that would make your score against a given field exactly average. It ignores your current rating, so it measures how you played in that event rather than how the event moved your official number.
How do you calculate performance rating?
Convert your percentage score into a rating difference using the FIDE conversion table, then add that difference to the average rating of your opponents. Fifty percent gives a difference of zero, so your performance equals the field average.
Why is performance rating undefined for a perfect score?
The formula would need an infinitely high rating to make a 100 percent score the expected outcome, so FIDE simply leaves the value undefined. The same applies to a zero score.
Does this match my online rating?
Chess.com and Lichess use Glicko-style ratings that track how certain the system is about your strength, so their changes differ from plain Elo, especially on a new account. This calculator implements the classical Elo arithmetic that FIDE uses.
