@oysteilo said in The new ELO-based ranking system:
maybe it is explained somewhere, but there are so many pages…Now I have a question about this formula

What is RB? Is it RBold? If it is RBold then what happens if two players with the same rating meet? Well then EA =1
R(B) is only used in context with R(A) to find the Expected Outcome (should A or B win). So yes it is R(B(old)) if you want to think of it that way.
And putting EA = 1 here makes no sense for the winning person:
EA = Expected outcome for Player A
If you have two players of equal rating, EA formula looks like this:
EA = 1 / { 1 + 10^[(RB - RAold)/F] }
RB - RAold = 0 since they are equal; formula then simplifies to:
EA = 1 / { 1 + 10^(0/F) }
10 ^ 0 = 1, so formula simplifies to:
EA = 1 / { 1 + 1 }
EA = 1/2
EA is always 1/2 for equal ratings, this conceptually is that they both have a 50% chance of winning.
EA will never equal 1, but it can get close to 1 if Player A is significantly higher rated than player B.
As an example, if A is rated 2250 and B is rated 750, and F is 500; we have:
EA = 1 / {1 + 10^[(750 - 2250)/F] }
EA = 1 / {1 + 10^[-1500/500] }
EA = 1 / {1 + 10^( -3) } = 1 / {1.001}
EA = .999 or 99.9% expected chance of Player A winning