# Elo rating system
**URL:** https://boards.straightdope.com/t/elo-rating-system/202069
**Category:** Factual Questions
**Created:** [September 17, 2003, 1:59am UTC](https://boards.straightdope.com/t/elo-rating-system/202069 "2003-09-17T01:59:12Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)
#### Post date: [September 17, 2003, 1:59am UTC](https://boards.straightdope.com/t/elo-rating-system/202069/1 "2003-09-17T01:59:12Z")
I know there’s a formula for this and google turns up tables of stuff. where can I find the formula with no reference tables? I remember doing this dring my M:TG days…
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### Author:  [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)
#### Post date: [September 17, 2003, 2:03am UTC](https://boards.straightdope.com/t/elo-rating-system/202069/2 "2003-09-17T02:03:32Z")
never mind, I found it…
All new players start out with a base rating of 1600. The DCI uses the following equation to determine a player’s win probability in each match:
```
1
```
Win Probability = --------------------------------------------------
10^((Opponent’s Rating–Player’s Rating)/400) + 1
This probability is then used to recalculate each player’s rating after the match. In the equation below, players receive 1 point if they win the match, 0 if they lose, and 0.5 for a draw. Players’ new ratings are determined as follows:
Player’s New Rating = Player’s Old Rating + (K-Value \* (Scoring Points–Player’s Win Probability))
All players are rated at the beginning with the first match in which they play. Further ratings are calculated chronologically from that first match.
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### Author:  [@Vriggs](https://boards.straightdope.com/u/Vriggs)
#### Post date: [September 17, 2003, 2:14am UTC](https://boards.straightdope.com/t/elo-rating-system/202069/3 "2003-09-17T02:14:56Z")
You are probably referring to the ELO expected score table, not the actual rating formula. If you want the rating formula (there are two - one for unrated/provisional players and another for previously rated palyers) you can get it [here](http://chess.ca/ratings_system.htm) (it’s a lengthy explaination).
Googling I found that the ‘expected score table’ is the mysterious table always referred to and is a normal probability function which is used to estimate the player’s strength distribution.
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### Author:  [@Tom\_Eaton](https://boards.straightdope.com/u/Tom_Eaton)
#### Post date: [September 17, 2003, 5:42am UTC](https://boards.straightdope.com/t/elo-rating-system/202069/4 "2003-09-17T05:42:52Z")
Nitpicking here, Vriggs, but I’ve seen a lot of people make the same error and it’s a pet peeve of mine: it’s not “ELO,” like the 70’s band, but “Elo,” namely Arpad Elo, the guy who devised the system.