FIDE rating tool

FIDE Rating Change Calculator

Enter the ratings, result and applicable K-factor. The calculator uses FIDE’s published score-probability table and the rating-difference rule effective from 1 October 2025. It shows a single game’s unrounded contribution, not a guaranteed next published rating.

What the calculation does

• Find the rating difference. For a player rated below 2650, a difference greater than 400 is counted as 400; at 2650 or above the full difference is used under the current rule.
• Look up the player’s expected score in FIDE table 8.1.2. The table works in one-percentage-point steps.
• Subtract expected score from the result: 1 for a win, 0.5 for a draw, 0 for a loss.
• Multiply by K. FIDE sums these contributions across the rating period and rounds the period change to the nearest whole number.

Choosing K

There is also a rating-period safeguard: if K multiplied by the number of games exceeds 700, FIDE reduces K to the largest whole number for which the product does not exceed 700. A one-game calculator cannot know that final adjustment unless you supply the whole period.

K = 40

New to the list until completing events with at least 30 games

K = 40

Through the end of the year of the player’s 18th birthday, while rated below 2300

K = 20

Rated below 2400 when neither K=40 condition applies

K = 10

Once a published rating has reached 2400; it remains 10 if the rating later falls

Sources and scope

• FIDE Rating Regulations, table 8.1.2 and articles 8.3.1–8.3.4.

Regulations and platform implementations can change. These notes were checked on 16 July 2026; follow the linked first-party source for the current wording.