What Is the Elo System?

The Elo rating system is the standard method for calculating the relative skill of chess players. Named after its creator, Hungarian-American physicist Arpad Elo, the system assigns each player a numerical rating that goes up when they win and down when they lose.

The key insight: the expected result of a game depends on the rating difference between the two players. A 400-point rating advantage means the higher-rated player is expected to score about 10 out of 11 games.


How Ratings Are Calculated

The Formula

After each game, both players’ ratings change based on three factors:

  1. The actual result — did you win (1 point), draw (0.5), or lose (0)?
  2. The expected result — based on the rating difference, what was the probability of winning?
  3. The K-factor — a number that determines how much ratings change per game
New Rating = Old Rating + K × (Actual Score − Expected Score)

Expected Score

The expected score is calculated using the rating difference. If Player A is rated 1600 and Player B is rated 1400 (a 200-point difference), Player A is expected to score about 0.76 (76%) and Player B about 0.24 (24%).

K-Factor

The K-factor determines rating volatility:

  • Higher K — ratings change more per game (used for new players so they reach their true level quickly)
  • Lower K — ratings change less per game (used for established players so ratings are more stable)

FIDE uses different K-factors: K=40 for new players, K=20 for established players, and K=10 for players rated above 2400.


Rating Ranges and Skill Levels

Rating Range Skill Level Description
Below 800 Absolute beginner Learning the rules and basic piece movement
800–1000 Beginner Knows the rules, makes many tactical errors
1000–1200 Experienced beginner Understands basic tactics, improving pattern recognition
1200–1400 Intermediate Solid tactical awareness, developing strategic understanding
1400–1600 Club player Good tactics, understands openings and basic endgames
1600–1800 Strong club player Consistent, understands planning and positional play
1800–2000 Expert-level Strong all-around player, deep strategic understanding
2000–2200 National Master (approx.) Top amateur level, competitive in national events
2200–2400 FIDE Master / International Master Professional level, strong opening preparation
2400–2500 International Master / Grandmaster Elite player, among the best in their country
2500–2700 Grandmaster World-class player
2700–2800 Super Grandmaster Among the best in the world
2800+ All-time elite Historically reserved for very few players

FIDE Titles

FIDE awards permanent titles based on rating achievements and tournament performance:

Title Abbreviation Typical Rating
Candidate Master CM 2200+
FIDE Master FM 2300+
International Master IM 2400+
Grandmaster GM 2500+

Titles above CM require not just a rating but also norms — exceptional performances in specific tournaments.


Rating Inflation and Deflation

A long-running debate in chess involves whether ratings have inflated over time. Key points:

  • Rating inflation — average ratings have increased over the decades, partly because better training and computer access make players stronger, and partly due to the influx of new players
  • Rating deflation — some argue that the talent pool is deeper, making it harder to achieve high ratings now than in the past
  • Comparison across eras — it’s difficult to compare Kasparov’s 2851 peak to Carlsen’s 2882 because the rating pools and competition levels differ

The consensus: ratings are best for comparing players within the same era, not across different time periods.


Online vs. FIDE Ratings

Online chess platforms use their own rating systems, which may differ from FIDE:

  • Online ratings tend to start and center differently than FIDE ratings
  • The rating distribution varies by platform
  • Online blitz ratings may differ significantly from online rapid or classical
  • FIDE ratings are based on over-the-board, in-person play

A good rule of thumb: online ratings and FIDE ratings are not directly interchangeable, but the relative ranking within each system is consistent.


History of the Rating System

  • 1939: The first chess rating system (the Harkness system) was adopted by the USCF
  • 1960: Arpad Elo proposed his improved system, which was adopted by the USCF
  • 1970: FIDE adopted the Elo system for international ratings
  • 2012: FIDE modified the system with different K-factors and more frequent rating updates

The Elo system’s influence extends far beyond chess — it is used in dozens of other competitive domains, from Go and Scrabble to video games, sports rankings, and even competitive programming.