ECF grading system

The ECF grading system is the name given to the rating system used by the English Chess Federation. A rating produced by the system is known as an ECF grade. The system is unique in both its methodology and the grades it produces.

It was first published in 1958, devised by Richard W. B. Clarke, father of politician Charles Clarke. Grades are updated on a six monthly cycle, based on results to the ends of June and December; before 2012 grades were published annually.

Every competitive game played under the ECF system results in a performance grade for each player, equal to

where n is the result of the game from their point of view (1, ½ or 0). For example, Player A who is graded 160 beats Player B graded 140. Player A's performance grade is 140 - 50 + (100x1) = 190; Player B's is 160 - 50 + (100x0) = 110. One player will lose as many points relative to their own grade as the other gains, thus ECF grades appear to be zero-sum when looking at a game in isolation; however, because the effect of any one game on a player's grade is inversely proportional to the number of games he or she plays, ECF grades are nonzero-sum overall.

There is one proviso in the calculation: grades more than 40 points different from one's own grade are considered to be exactly 40 points different when calculating performance grades. Had Player B's grade been 100, Player A would have scored 120 - 50 + (100x1) = 170, and Player B 140 - 50 + (100x0) = 90. This prevents players increasing their grade by losing to much higher-graded players and also means that the stronger player's grade cannot go down when winning.

At the end of a cycle, each player's performance grades for that cycle are averaged to give the personal grade used for the following period. If fewer than 30 games have been played, the most recent games from preceding cycles may be included in the average to make the number up to 30.

A specific weakness of rating systems is their treatment of junior players. Juniors tend to improve and therefore their rating/grading lags their current strength. The ECF grading system addresses this by inserting an additional stage into the process for those aged under 18. The system outlined above uses each player's grade from the previous cycle to calculate the performance grade. For juniors this performance grade is recalculated based on performance grades obtained over the previous year (including the recalculation of grades of junior opponents). It is this recalculation that becomes the performance grade for the final calculation for all players.

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