elo rating

The Elo rating system is a method for calculating the relative skill levels of players in zero-sum games such as chess. It is named after its creator Arpad Elo, a Hungarian-American physics professor.

ELO is often written in all caps but it doesn’t have a full form — it’s simply named after its creator Arpad Elo, a Hungarian-American physics professor born in 1903.

The Elo rating system is a rating system for two-person, zero-sum games based on the assumption that performance is normally distributed. That is, a player's performance is expected to follow a normal distribution. For FIDE the mean = the player's rating and standard deviation = 2000/7 = 285.7.

Most people associate Elo with the game of chess — it is used extensively by national chess federations, online chess websites, and even by FIDE (the governing body of international chess competitions) to determine the world rankings of Chess players. In fact, Arpad Elo was a chess master himself.

But the Elo rating system is also used in A LOT of other games, including basketball, american football, rest-of-the-world football, baseball, board games such as Scrabble, and even video games such as Overwatch.

A player's Elo rating is represented by a number which may change depending on the outcome of rated games played. After every game, the winning player takes points from the losing one. The difference between the ratings of the winner and loser determines the total number of points gained or lost after a game. If the high-rated player wins, then only a few rating points will be taken from the low-rated player. However, if the lower-rated player scores an upset win, many rating points will be transferred. The lower-rated player will also gain a few points from the higher rated player in the event of a draw. This means that this rating system is self-correcting. Players whose ratings are too low or too high should, in the long run, do better or worse correspondingly than the rating system predicts and thus gain or lose rating points until the ratings reflect their true playing strength.

An Elo rating is a comparative rating only, and is valid only within the rating pool where it was established.

Generally speaking, you can imagine the Elo rating like a quick system to tell how strong is a player. So for instance, Magnus Carlsen (currently the World Champion) has a rating of about 2840 points. 

While there is no theoretical limits in the Elo system, you can set the boundaries more or less to 1300 (for weak players) and to 2850 (for the top players in the World). The highest Elo ever was 2889, reached by Magnus Carlsen in 2014. Carlsen himself could not keep that rating for very long, and as I said he’s currently below 2850. Still the number 1 in the world though!

• FIDE has its own gradation of the chess players based on ELO ratings. Here is an approximate table:

  • >2,700 – Grandmaster qualifying for the world championship match
  • 2,500-2,700 – Grandmaster (GM)
  • 2,400-2,499 – International Master (IM) or Senior Master
  • 2,200-2,399 – National Master (NM)
  • 2,000-2,199 – Expert or Candidate Master
  • 1,800-1,999 – Class A
  • 1,600-1,799 – Class B
  • 1,400-1,599 – Class C
  • 1,200-1,399 – Strong Beginner

  • In order to obtain a FIDE norm of Grandmaster (GM) or International Master (IM) the following conditions must be true:

    1. A minimum of 9 games should be played

    2. At least 50% of opponents must be titled players

    3. The players score must be equal or higher than minimum performance rating needed for the norm (2600 – GM norm, 2450 – IM norm).

    4. For GM norm at least 30% of the players played must be GMs

    5. For IM norm at least 30% of the players played must be IMs. In order to achieve a National Master (NM) norm, it’s only needed to obtain a certain rating (2300).

  • 1,000-1,199 – Beginner
  • <1,000 – New player
  • 100 – Minimal possible ELO rating