How chess ratings work, and why we use Elo

Your rating is the site's best guess at how you will score against other players. It is not a grade, and it is not a measure of how much you know. It is a prediction that gets checked after every game.

The Elo idea

The system most players know was designed by physics professor Arpad Elo in the 1960s and adopted by FIDE in 1970. Its core rule fits in one sentence: the bigger the rating gap, the more points the stronger player is expected to score.

After a game your rating moves by how much you beat or missed that expectation. Beating a much stronger player moves you a lot. Beating a much weaker one barely moves you at all.

How fast your rating moves

How far one game moves your rating is set by a number called K. Your change is K times the difference between your result and the expected score: 1 for a win, 0.5 for a draw, 0 for a loss.

Say you are rated 1500 and you play someone rated 1700. You are expected to score about 0.24.

Your first 30 rated games at each speed use K = 40, so a new account gets to its real level quickly. After that K drops to 20 and one game moves you half as much. FIDE also gives new players K = 40 for their first 30 games. Until those first 30 games are done we show your rating with a question mark, for example 1500?, so opponents know it is still settling.

Why not Glicko-2?

Lichess uses Glicko-2, designed by statistician Mark Glickman. Next to the rating it keeps a deviation, how unsure the system is about you, and a volatility, how consistent your results are. It is a fine system, and it handles players who come back after a long break better than Elo does.

We chose Elo because you can check it yourself: one number per speed and one formula, the same one used for over-the-board ratings. The higher K for your first games gives new players the quick start that Glicko-2 gets from its deviation.

How we use it

You get a separate rating for each speed, because being good at one-minute bullet says little about thirty-minute games:

• Bullet: games expected to last under about 3 minutes
• Blitz: under 8 minutes
• Rapid: under 25 minutes
• Classical: anything longer

The expected length counts the starting time plus forty moves' worth of increment, so 3+2 counts as blitz and 15+10 as rapid. Puzzles get their own rating too, because solving a puzzle is a different skill from playing a game. Ratings never drop below 100.