Elo calculator for chess and other games
The Elo calculator shows at once how your rating changes after a game or a whole series: enter your rating, your opponent’s rating and the result, choose the K-factor, and you see the expected score and your new rating. The values shown are examples.
Source: FIDE Handbook B.02: Rating Regulations (valid from 1 Mar 2024) – K-factor, difference above 400, expected score. Updated: .
How it is calculated
How the Elo calculator works
An Elo rating predicts how many points one player scores against another. From the rating difference D (your rating minus your opponent’s) the expected score follows: E = 1 / (1 + 10−D/400). With equal ratings E is 0.5, with a 100-point lead about 0.64, with 200 about 0.76. After the game your rating changes by K × (result − E): a win counts 1, a draw 0.5, a loss 0. Whoever scores more than expected gains points and the opponent loses exactly as many.
The K-factor
K decides how much a single game matters. Under the FIDE rules (in force from 1 March 2024) K = 40 for new players until 30 games and for players up to the end of the year of their 18th birthday while rated below 2300; K = 20 while the rating stays below 2400; K = 10 once 2400 has been reached. Clubs and online platforms often use their own values such as 16, 24 or 32 – pick the K of your federation.
Several games
Add more games in the box below. “Rating period” calculates all games against your starting rating, as FIDE does for a tournament. “One after another” updates the rating after every game, as many online platforms do; the result then differs slightly.
Limits
FIDE uses a conversion table for E rather than the formula; the values differ by at most about 0.01. A rating difference above 400 counts as 400 at FIDE (for players below 2650), which the calculator mimics with a tick box. Platforms such as Lichess or Chess.com use their own systems (Glicko), so their numbers will not match exactly. Time per game is handled by the chess clock, you can play the computer on the chess computer, the tournament planner helps with events, and the score keeper counts points.
Frequently asked questions
How do you calculate the new Elo rating?
New Elo = old Elo + K × (result − expected score). The expected score comes from the rating difference: E = 1 / (1 + 10^(−D/400)).
Which K-factor should I use?
At FIDE 40 for new players (first 30 games) and juniors under 2300, 20 below 2400 and 10 from 2400. Federations and platforms may use other values.
What is the win probability at a 100 Elo difference?
The stronger player expects about 0.64 points per game, about 0.76 at 200 Elo and about 0.91 at 400 Elo. Draws count half.
Can I calculate a whole tournament?
Yes. Enter the games in the “More games” box, one per line, for example 1800:1. The calculator adds up the changes.
Why does my official rating differ?
FIDE uses a conversion table, rounds and applies special rules; platforms often use other systems. The calculator gives the standard Elo formula.
Sources and legal basis
- FIDE Handbook B.02: Rating Regulations (valid from 1 Mar 2024) – K-factor, difference above 400, expected score
- Wikipedia: Elo (en)
As of: · Editorial policy
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