# Computer Chess Club Archives

## Messages

### Subject: Re: ELO performance?

Author: Peter Fendrich

Date: 10:58:43 05/22/99

Go up one level in this thread

```On May 22, 1999 at 12:53:55, Stefan Meyer-Kahlen wrote:

>Just two questions concerning ELO performance and probabilities:
>
>* How do I calculate my ELO performance if I get x percent out of y games
>against an opponent with z ELO points?
>
>* In which range is my own ELO rating with 95% probability after that match?
>
>I guess those are FAQs with 95% probability :-)
>
>Thanks
>   Stefan

ELO is about rating difference and not the actual ELO rating.
The performance formula is:
Rp = Rc + D(P)
where Rp is your rating before the match, Rc is your opponents
rating before the match and P is the percent score (in your case=x).
D(P) is the rating difference that P indicates. That means that P indicates what
rating difference would be excpected with such a result.
It is possible to compute D(P) with the help of a Bell curve but the easy way is
a lookup table.

Give me an email and I will give you the table or the formula whatever you like.

//Peter

```

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