Originally posted by gregoftheweb
How are the ratings from a draw calculated? I can put another button on that tool.
This is from the pop up help FAQ.......
Players are rated using the following formula:
New Rating = Old Rating + K * (Score - Win Expectancy)
K is a constant (32 for 0-2099, 24 for 2100-2399, 16 for 2400 and above)
Score is 1 for a win, 0.5 for a draw and 0 for a loss.
The Win Expectancy is calculated using the following formula:
Win Expectancy = 1 / (10^(( Opponent Rating - YourRating) / 400)+1)
The Win Expectancy is used in the rating calculation but is interesting on its own. For example, the calculation below is for a rating difference of 200. This shows that if you have a rating 200 points higher than another player, you can expect to beat them, on average, three times for each four games played.
Win Expectancy = 1 / (10 ^ (-200 / 400)+1) = 0.76
Note: ^ = "to the power of", e.g. 2^3=8.
Hope that helps... It's all greek to me... otherwise known as math.