# Computer Chess Club Archives

## Messages

### Subject: Re: ELO performance?

Author: Peter Fendrich

Date: 15:35:13 05/23/99

Go up one level in this thread

```On May 22, 1999 at 21:27:34, Robert Hyatt wrote:

>On May 22, 1999 at 18:11:52, Peter Fendrich wrote:
>
>>On May 22, 1999 at 15:25:52, Robert Hyatt wrote:
>>
>>>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
>>>
>>>
>>>Performance rating is trivial.  compute the following:
>>>
>>>number_wins * (opponent's rating +400)
>>
>>This is not the *ELO* performance rating but probably one of all the national
>>variation that there is...  USCF?
>>
>>//Peter
>>>number_draws * opponent's rating
>>>number_losses * (opponent's rating - 400)
>>>
>>>add those up, divide by number of games.
>>>
>>>there is no "95%" probability for a performance rating...
>
>
>That is the only "performance rating" formula I have ever seen used.  There are
>alternative ways to represent it... ie
>
>TPR = opponents_rating + (400*(W-L))/N
>
>and so forth.. but they are all the same.  If you know of another one, please
>post it...  (btw "elo performance rating" doesn't (to me) imply that this is
>in Elo's book, just that it is an estimated "Elo rating" based on nothing but

That's true and the elo performance rating formula below is just that.
What you are proposing is a linear approximation of the Performance Rating.
It is not USCF as I thought. In fact it is also mentioned by Dr. Elo.
The purpose with this, from what I can understand, is to easyly calculate the
performance rating by hand.
The original performance rating is:
Rc + D(P)
where Rc is the opponents average rating. D(P) is the expected rating difference
with the current win percentage P. D(P) is based on the Bell curve.

//Peter

```