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.
Calculation of rating
Every competitive game played under the ECF system results in a performance grade for each player, equal to
- Opponent's grade - 50 + 100n
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 (but because this applies whatever the result, as a side-effect it protects stronger players by lessening the impact of a defeat by a much lower-graded player).
At the end of a season, each player's performance grades for that season are averaged to give the personal grade used for the following season. If fewer than 30 games have been played, the most recent games from the two preceding seasons may be included in the average to make the number up to 30.
In theory a non-chess player would have a grade of 0; in practice negative grades exist but are set to 0 on the grading list. The weakest adult club players come in at about 40. A three-figure grade is a source of prestige among casual players, while those who seriously study the game may try to break 150. A player graded over 200 is usually well known outside his or her area and might consider aiming for a master title. Grades far in excess of 200 lose their significance as very strong players tend to play mostly in internationally rated tournaments.
The name of the 150 Attack, a no-nonsense response to the Pirc Defence popularised by British players, comes from the ECF grading system. According to Sam Collins in Understanding the Chess Openings this is because "even a 150-rated player could handle the White side".
Prior to 2005 grades in England were administered by the former British Chess Federation and were called BCF grades.
Conversion to and from Elo ratings
Although the ECF grading system is mechanically very different from the Elo rating system, the ECF publishes formulae that can be used to estimate the equivalent ECF grade of an Elo-rated player, and vice versa:
Prior to 2014, there were separate formulae for converting FIDE ratings (F) and Elo ratings given by national chess organisations (N):
The ECF does not use FIDE or other Elo ratings in calculating players' grades. Rather, the formulae are provided as guidance for tournament organisers.