What Does ELO Stand For?

What does ELO stand for in chess?

In chess, Elo is a rating that measures how strong a player is compared with other rated players. It is named for its creator, not built from initials, so there is no hidden phrase behind E, L and O. A higher number means a stronger player.

Arpad Elo worked out the system in the 1950s and 1960s to fix problems with older chess rating methods. The United States Chess Federation adopted it in 1960, and the world chess federation took it up in 1970. It soon spread far beyond chess. Today you will find versions of it in board game clubs, college sports power rankings and the matchmaking of many online games.

Since Elo is a name, it is not really an acronym at all. Writing ELO in all capitals is a common mistake, a bit like writing a person's last name in capitals because it looks like code.

How Elo points move after a game

The idea is simple. Before a game, the two ratings predict who should win. After the game, each player gains or loses points based on how the result compares with that prediction.

• Beat a stronger player: you gain a lot, because the system did not expect it.
• Beat a weaker player: you gain only a little, because that was the likely result.
• Lose to a weaker player: you drop more than you would against a stronger one.
• Draw: the lower rated player usually gains a few points and the higher rated player loses a few.

Points move from one player to the other, so the loser's drop matches the winner's gain in the basic system. A number called the K factor sets how big each swing can be. New players often get a larger K factor so their rating finds its true level faster.

What the numbers roughly mean

Every rating pool is a little different, so the same number can mean slightly different things in different places. As a loose guide for over the board chess:

A rating is a comparison, not a grade. Ratings on online chess sites and in games often run higher or lower than federation ratings, so it is best to compare numbers only within the same system.

Elo in video games and sports

Many competitive games use an Elo style system, sometimes changed a lot, to pair players of similar skill. Players talk about their "Elo" even when the game calls it something else, such as a hidden matchmaking rating.

• "I climbed 100 Elo this weekend."
• "Low Elo games are chaotic."
• "Her Elo is high enough to enter the open section."
• "The app pairs you by Elo, so the matches feel close."

Sports writers also use Elo ratings to rank teams in soccer, basketball and football, giving a team more credit for beating a strong opponent than a weak one.

Other ELO meanings and look-alikes

Outside games, the capital letters can point to other things.

• Electric Light Orchestra: a British rock band, almost always called ELO.
• A short form in job ads or schools: some groups use ELO for their own program names, so check the context.

Do not mix up an Elo rating with an IQ score. Both are numbers, but IQ comes from a test, while Elo comes only from game results against other players. A sports MVP award, likewise, is a vote, not a rating. Many more short forms sit in the famous acronyms collection.