How to use
- 1Choose FIDE (chess) or generic Elo and enter your rating.
- 2Pick your K-factor, or tick the boxes under “Find your FIDE K-factor” if you are unsure.
- 3Add each game with the opponent’s rating and the result (1, ½, 0) — a whole tournament if you like.
- 4See the expected score and change for every game, plus the total change and your new rating.
FIDE K-factor and the 400-point rule
Under the FIDE Rating Regulations in force since 1 March 2024: K = 40 for a player new to the list until they have completed 30 games, and for juniors until the end of the year of their 18th birthday while rated under 2300; K = 20 while rated under 2400; K = 10 once a published rating has reached 2400, even if it later drops. If K × games in one rating period exceeds 700, K becomes the largest whole number that keeps it at 700 or below. Since 1 October 2025 a rating gap over 400 counts as 400 only for players rated below 2650.
How the calculation works
For each game the change is K × (result − expected score). In FIDE mode the expected score comes from the regulations’ table 8.1.2 — a 100-point gap gives the stronger player 0.64 — and the period total is rounded to a whole number. Generic mode uses the classic logistic formula 1 ÷ (1 + 10^((opponent − you) ÷ 400)) with any K you choose, which suits club ladders, online games or your own five-a-side or tennis rankings.
National ratings
Many federations run a separate national grade — the ECF rating in England or US Chess ratings in the United States — with their own formulas and K-factors. This tool calculates FIDE ratings and generic Elo only. FIDE publishes a new rating list every month; the change shown here is what a finished tournament will add to your next list.
Frequently asked questions
How is Elo rating calculated?
Rating change = K × (actual score − expected score). The expected score depends on the rating difference and is 0.5 between equally rated players.
What K-factor does FIDE use?
40 for new players (first 30 games) and juniors under 18 rated below 2300, 20 for players under 2400, and 10 for anyone whose rating has reached 2400.
What is the 400-point rule?
A rating difference larger than 400 is treated as 400. Since October 2025 the rule applies only to players rated below 2650.
Do you gain rating points for a draw?
Yes, if your opponent is rated higher. The lower-rated player gains and the higher-rated player loses; the size depends on the gap and K.
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