http://gobase.org/studying/articles/elo/ im confused about the elo difference. what if the difference is 30 or 150? so I round to nearest elo difference or is there some formula to calculate the elo difference?

There is a formula. E = 1 / ( 1 + 10r/s.d. ), where E is the expected result, r is the +/- ratings difference, and s.d. is the standard deviation). For USCF, s.d. is 400. I'm not sure where the table in that article came from. Here is a more precise table (for chess): Chess Ratings. For more information, look at the Wikipedia entry: Elo Rating System

[Edited by - JohnBolton on September 3, 2006 2:56:56 AM]