Glicko Ratings Explained: A Practical Guide for Organizing Friendly Competitions

What Is the Glicko Rating System?

The Glicko rating system is a method for calculating the relative skill levels of players in two-player games such as chess, Go, or online multiplayer games like Dota 2. Developed by Mark Glickman as an improvement over the older Elo system, Glicko introduces a measure of rating uncertainty called the rating deviation (RD). The core idea is simple: a player’s rating is not a fixed number but a range of possible values. The system becomes more confident in a player’s rating as they play more games, and it adjusts more aggressively for players with high uncertainty.

Unlike Elo, which uses a single number and assumes a constant level of certainty, Glicko tracks both a rating and an RD. A high RD means the system is unsure about the player’s true skill (e.g., a new player or someone returning after a long break), so their rating can change dramatically after a few games. A low RD means the rating is stable and will change only slightly after each game. This makes Glicko particularly well-suited for groups of friends who play irregularly—ratings adapt quickly when someone improves or gets rusty.

How Does the Glicko Rating System Formula Work?

The Glicko rating system formula is an extension of the Elo formula. For a given game between two players, the expected score (win probability) is calculated using their ratings and RDs. After the game, each player’s rating and RD are updated. A player’s new rating is a weighted average of their old rating and the game result, with the weight depending on their own RD and the opponent’s RD. Players with high RD (uncertain) will have larger rating changes; players with low RD will have smaller changes.

The system works over rating periods, which can be a single tournament, a set of games, or a fixed time interval. Within a rating period, all games are considered simultaneously; the player’s rating and RD are updated once at the end of the period based on all results. This prevents the order of games from biasing the ratings, a common issue in dynamic Elo implementations.

The key parameters are:

• Rating (R): The player’s estimated skill level.
• Rating Deviation (RD): The standard deviation of the rating, measuring uncertainty. Typically, RD starts at 350 for new players and decreases over time, with a minimum around 30–50.
• Volatility (σ): A measure of how much a player’s rating fluctuates from period to period (introduced in Glicko-2, the improved version). A higher volatility means the player’s skill is changing unpredictably.

In Glicko-2, an additional step estimates the player’s volatility before updating the rating and RD, making the system more responsive to players whose performance changes over time.

Glicko Rating Scale and Interpretation

The Glicko rating scale is similar to Elo in practice. A rating of 1500 is often considered average for a beginner or casual player, 2000 is a strong club player, and 2500+ is expert or master level. However, because of the RD, a Glicko rating should always be interpreted with its uncertainty. For example, a rating of 1500 ± 200 means the player’s true skill is likely between 1300 and 1700. A rating of 1500 ± 30 means we can be quite confident they are close to 1500.

For organizing a friendly event, you don’t need to worry about absolute scale. You just need a consistent starting point. Most systems initialize players with a rating of 1500 and an RD of 350. After about 10–20 games, the RD typically drops to a stable level (below 100), and ratings become meaningful relative to the group.

Glicko vs Elo: What’s the Difference?

In short, Glicko is more robust for irregular play and varying levels of activity, making it ideal for a group of friends who may not play every week. The Glicko rating system vs Elo debate usually comes down to this: Elo is simpler, but Glicko is more accurate when players have different activity levels or when new players join frequently.

Using a Glicko Rating Calculator for Your Group

You don’t need to compute the formulas by hand. There are many free online Glicko rating calculator tools and spreadsheets available. To use one, you typically need:

1. Each player’s current rating and RD.
2. The results of all games in the rating period (e.g., who beat whom).
3. The calculator will output updated ratings and RDs.

If you’re setting up a system for your group, you can:

• Use a simple spreadsheet with Glicko formulas built in (many templates exist).
• Use an online rating tracker service (some are free for small groups).
• For Dota 2 or other games that already use Glicko internally, you can simply use the game’s own matchmaking rating as a seed.

For a friendly tournament, you might only need to compute ratings once after the event, or you can maintain an ongoing leaderboard after each session.

Organizing a Tournament with Glicko Ratings

Now, let’s turn to the practical side: how to organize a tournament for your group of friends, using Glicko ratings to make it fair and fun.

Step 1: Set Up the Rating System

Decide how you will compute ratings. If you’re just starting, assign everyone an initial rating of 1500 and RD of 350. Use a Glicko-2 rating system calculator (or a spreadsheet) to update ratings after each round or after the whole tournament. If you have existing data from casual play, you can use that as a starting point.

Step 2: Choose a Tournament Format

For a group of friends, common formats include:

• Round-robin: Everyone plays everyone. Best for small groups (up to 8 players) because it gives many games and clear standings.
• Swiss system: Players are paired each round based on current standings; no one is eliminated. Good for larger groups (8+).
• Double elimination: Players are out after two losses. Good for a more competitive feel but can be long.

For beginners, a Swiss or round-robin is recommended because everyone gets to play the same number of games, and the ratings update meaningfully.

Step 3: Build the Bracket or Schedule

If using round-robin, create a schedule using a circle method: assign each player a number, and rotate the matchups each round. For Swiss, use a simple pairing algorithm: in each round, pair players with similar current scores (win/loss record). For double elimination, draw a standard bracket, seeding players by initial rating if available.

Example: 8 players, round-robin = 7 rounds, each player plays 7 games. With 4 players, it’s 3 rounds. Keep the total number of rounds manageable for the time you have.

Step 4: Plan a Realistic Schedule

Consider the average game length for your activity. For chess, a casual game might take 30 minutes. For Dota 2, a single match can take 40–60 minutes. Plan breaks between rounds (10–15 minutes) and a longer break for food if needed. A half-day event can accommodate about 4–6 rounds of 30-minute games, or 3–4 rounds of 1-hour games. Be realistic and avoid overloading—friends want to socialize too.

Step 5: Communicate the Format and Next Round

Before starting, explain the rules: how ratings are calculated (briefly), how pairings are made, and how standings are determined. After each round, post the updated standings and the next round’s pairings visibly—on a whiteboard, a shared online document, or a messaging group. This keeps everyone informed and reduces confusion.

Step 6: Update Ratings After the Event

After all games are played, input all results into your Glicko calculator for the final rating period. Update each player’s rating and RD. Publish the final leaderboard and, if you plan to continue, keep the ratings for the next event. The RD will naturally decrease as players play more, making ratings more stable over time.

Practical Example: 6 Friends, Swiss Tournament, Chess

Suppose you have 6 players. You choose a Swiss system with 4 rounds. Initial ratings: all 1500, RD=350. Round 1 pairings are random. After each round, you update scores and pair players with similar scores. At the end, you have 4 games per player. Use the Glicko calculator to update ratings. A player who went 3-1 will see their rating increase and their RD drop to around 150–200. A player who went 0-4 will drop and also see RD decrease because they played many games. Next time, the ratings will be more accurate.

Common Questions and Adjustments

What if someone misses some rounds? In Glicko, their RD increases between rating periods to reflect increased uncertainty. You can simply skip their games and let the calculator handle it, or assign them a bye (no change).

What about new players joining later? Start them at 1500 with RD=350. They will be rated quickly after a few games.

Can I use Glicko for team games like Dota 2? Yes, the Glicko rating system Dota 2 is used in matchmaking. For a friendly tournament, you can rate individual players based on their team’s results, or rate teams as units. Individual ratings are more granular but require more complex modeling if teams change between games.

By following these steps, you can turn a casual group of friends into a well-organized competitive event with fair and dynamic ratings. The Glicko system provides a solid foundation, and the tools are accessible to anyone.