It isn't really that much at less than 100 points. You can do it directly using what's sometimes called the 400 point rule. Add up the ratings of your opponents, add or subtract 400 times your excess or otherwise of wins over losses, divide by the game count. If the method sounds familiar it's because the old Otto Clarke system is a linear approximation to Professor Elo's version which used probability tables.Peter Harrington wrote: ↑Tue Aug 16, 2022 12:23 pmAnd this is what I was expecting to see, and 1563 is much better than 1477.
The Elo performance measure is that rating which gives an expected score of what you achieved against the opposition you faced. Another point is that the figures shown by the chess-results sofware aren't always reliable. Better to see what the ecfrating system comes up with. Incidently that could be accused of slacking in not yet having the results of the completed tournaments, but perhaps they are waiting for the Congress as a whole to complete.
(edit) There may be a simpler explanatuion. The chess-results calculations may be using the International ratings, and not all your opponents had them and in any event they are mostly different from the max(Elo,English) used in the pairings. (/edit)