US Chess rating calculator

These are the formulas of The US Chess Rating System, the document by Mark E. Glickman and Thomas Doan that defines how US Chess rates events, in its revision of 6 April 2026. The same formulas rate the Regular, Quick and Blitz systems, over the board and online, each separately.

1. Effective games. How much your rating can move depends on how sure it is, written as an effective number of games, N′: the smaller of your rated games and

   N* = 50 / √(0.662 + 0.00000739 × (2569 − rating)²)

   which is 50 from 2355 up. A 1700 player with 30 games has N′ = 20.
2. Standard formula. For a rating that rests on more than 8 games, each game's expected score is

   E = 1 / (1 + 10^{(opponent − you) / 400})

   and

   K = 800 / (N′ + m)

   where m is the number of games in the event. Your rating moves by K × (score − expected).
3. Bonus. In an event of at least 3 games, with no opponent played more than twice (more than once in a 3-game event), whatever K × (score − expected) exceeds 10 × √m is added again, with m counted as 4 for a 3-game event. The multiplier has been 10 since 1 January 2025.
4. Special formula. For a rating that rests on 8 or fewer games, or a player who has won every game or lost every game so far, the new rating is the one at which a linear expectancy, 0.5 + difference ÷ 800 from 0 to 1, adds up to your score. Your earlier games count too, as N′ games against your old rating with half the points won; after all wins they count as all won against a rating 400 lower, after all losses as all lost against a rating 400 higher. A win never lowers the rating and a loss never raises it. The result is at most 2700.
5. Dual-rated events. For a Regular rating above 2200, in an event at a time control from 30 to 65 minutes, K is 800 × (6.5 − 0.0025 × rating) / (N′ + m) below 2500, and 200 / (N′ + m) from 2500.
6. Floors. No rating goes below 100. An established player has a floor 200 points below their highest established rating, rounded down to the hundred, from 1200 to 2100.
7. First rating. A player with no US Chess, FIDE or Canadian (CFC) rating starts from 50 × their age, at most 1300. That estimate only breaks ties: the first event is rated with the special formula and N′ = 0, so the games themselves set the rating. Another rating, where there is one, is converted and used instead; this calculator does not do that conversion.

US Chess rates each event in two passes, the second against the opponents' ratings after the first, and keeps ratings to several decimals. This calculator works from the ratings before the event, so the official result can differ a little.