the punters lab
The Elo ratings calculator
|How it works
You give the elo rating of the home team and the elo rating of the away team and also check if the venue is neutral or not (it is initially set as "non neutral"). The java script computes the probabilities of the home-draw-away for the 90 minutes of play, also the probabilities after extra time (+ penalties) - if that applies.
The fair prices are also computed (the prices that correspond to hypothetical take off percentage of 0%).
(*) to check the functioning of the calculator, try some numbers between 1500-2000 (the typical range of the elo ratings).
The elo rating represents the basic strength of a football team.
Their theory is explained here.
There are two types of football elo ratings: For the national teams and for the clubs.
What we have done here was to make use of the available data, ratings and results, to construct a probability scale so we can compute the probabilities of the three possible outcomes (1-X-2).
The venue also plays a role. When the venue is neutral the probability of the -nominal- home win is less than if the venue is non-neutral (and correspondingly the probability of the away win is bigger).
To find the elo ratings of teams that interest you, you go to the elo tables in the following webpages:
eloratings.net (for national teams)
clubelo.com (for clubs)
In these pages the elo ratings are archived and also renewed after every match.
Some usual questions
What do I do if the team has no Elo ? This can happen with the clubs. In such cases we recommend you find a team of the same country that has been assigned an Elo rating and is at roughly the same position in the league table as the one you are looking for. If two teams differ by one point in the home league table, their elo ratings differ by 10.5 points - approximately.
Do the elo ratings tell all the story ? Usually they do, but for matters like player injuries, suspensions, motivation, you should also have a look into the sports news (*).
Is there a better method ? We are not responsible for the creation of the ratings -only for the mathematical formulas that derive from those- but the method is fairly good. However in the CosmiC Football Predictor software (see here) we use better performing enhanced elo ratings.
What is the probability formula ? The formula is a complicated spline function and is the result of function fit we performed using the old ratings and the old results available.
(*) It's a fact that the study of a football match, to work out the prices, has two stages:
First the mathematical analysis and second the qualitative analysis.
The mathematical analysis is the elo ratings -or equivalent ratings.
But some times there are special conditions that alter the probabilities (e.g. absences, injuries). So even a complete reversal is possible (e.g. when one of the two teams decides to play with their amateur squad).