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.
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 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.
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".
Due to the inherent simplicity of the ECF Grading System, one of the benefits it has over the ELO rating system used by FIDE, is the ability to calculate performance grades before, or after the game result without the need for specialist software or a calculator.
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 FIDE Elo rating, and vice versa:
The ECF grading system was recalibrated in 2009. Various other conversion formula have been used, but usually relate to the prior scale.
The conversion is used to grade some games played outside the Federation where opponents do not have an ECF grade. It is designed to give a best estimate conversion. It is often used by organisers of English congresses to determine qualification for grading restricted events when a player has an Elo rating, but no ECF grade. It is not ideal in this circumstance, since about half the conversions will be too low.