An EFC rating of 900 is impossibly high. They run from near-zero to something under 300.
There are several formulae for converting EFC to FIDE (or vice versa), differing in minor details.
North Staffs League uses : EFC x 7.5 + 700 = FIDE so a 90 EFC would be 1375 FIDE.
This same formula (EFC x 7.5 + 700 = FIDE) is mentioned in the Wikipedia.
Okay thats great, I thought 900 seemed way off. What would you say 1700 on chess.com would be for FIDE if you had to guess
There's really no way to compare chess.com ratings with FIDE ratings. A rating is not a number handed down by God. It's a calculated score based on your past performance AGAINST A SPECIFIC POOL OF PLAYERS... those players who make up the rating pool that you interact with.
The great majority of chess.com players are not FIDE rated, so the two rating pools are seperate and distinct. That means that the two ratings don't connect.
Having said that... if you still want a conversion factor, try subtracting 125 points from the chess.com rating and calling it "FIDE equivalent". But be warned, I just pulled that number out of my butt.
Would anyone be able to tell me a 900 ECF rating is equivalent to on cehss.com or FIDE ?
Thanks