How ratings work

The Chesspirit rating is an internal rating computed with the Elo method, with coefficients close to FIDE's. It is always called “Chesspirit rating”, never just “Elo”, to avoid confusion with the official list.

The formula

After each game, the actual score (S: 1 for a win, ½ for a draw, 0 for a loss) is compared with the expected score (E), which depends on the rating gap.

E_A = 1 / (1 + 10^{(R_B − R_A) / 400})

R′_A = R_A + K × (S − E_A)

The K factor

K = 40: fewer than 30 games, or under 18 with a rating below 2300.
K = 20: general case.
K = 10: players who have reached 2400.

Principles

Four ratings per player: over-the-board blitz, rapid and classical, plus a separate online rating.
Only Chesspirit-rated tournaments change over-the-board ratings; forfeits do not count.
Players with a FIDE rating start at their FIDE rating in that time control; others start at 1200, a provisional rating replaced by their performance after 5 games.
Rating changes for a tournament are computed from pre-tournament ratings, then rounded.
The calculation can be replayed from the full game history: an approved correction triggers a recalculation. The official list is published on the first day of each month.

Check a calculation

Your rating

Opponent's rating

Result

Games already played

Age

Peak rating

E: 0.360
K: 20
Δ: +12.8
New rating: 1513