Handbook  B. Permanent
Commissions  02.
FIDE Rating Regulations (Qualification Commission)  14.0. Some comments
on the Rating system
14.0. Some comments on the Rating system
14.1 
The following formula gives a close approximation to tables
10.1a/b.
P = 1/(1 + 10  [D/400]). However the tables are used as shown.

14.2 
Tables 10.1a/b are used precisely as shown, no extrapolations
are made to establish a third significant figure. 
14.3 
K is used as a stabilising influence in the system. When K =
10, the rating turns over in approximately 75 games, K = 15, 50 games, K = 25 it
is 30 games. 
14.4 
The system has been devised to enable players to verify their
ratings readily. It would be more accurate to rate each game separately as
averaging assumes a linear scale. However this would be much more laborious.
 
