Elo Rating Calculator
Use this Elo rating calculator to work out the new ratings for two players or teams after a match. Originally built for chess, the Elo system is now used across sports, esports and board games. Enter both current ratings, the result, and a K-factor, and the calculator returns each player's expected score and their updated rating.
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Calculate new Elo ratings
Enter values above and press Calculate to see your result.
Formula used
Each player has an expected score based on the rating difference:
Expected A = 1 ÷ (1 + 10^((Rating B − Rating A) ÷ 400))
After the game, ratings move toward the actual result (1 = win, 0.5 = draw, 0 = loss):
New A = Rating A + K × (Score A − Expected A)
The K-factor sets how much a single game moves the rating. Beating a higher-rated opponent gains more points than beating a lower-rated one, because the win was less expected.
Worked examples
Upset win. A 1500 player beating a 1600 (K=32) was expected to score ~36% — the win adds about +20, to 1520.
Expected win. A 1600 beating a 1500 gains only about +12, since the win was likely.
Draw. A draw still shifts ratings toward each other when one player was favoured.
How to use this calculator
- Enter both players' current ratings.
- Choose the result from Player A's perspective.
- Set the K-factor for your league or skill level.
- Press Calculate for the expected scores and new ratings.
- Apply the same K-factor consistently across a rating pool.
Choosing a K-factor
| K-factor | Use for | Effect |
|---|---|---|
| 40 | New / provisional players | Ratings move quickly to find their level |
| 20–32 | Most amateur play | Balanced responsiveness |
| 10–16 | Masters / established ratings | Stable, slow to change |
Higher K means more volatility; lower K means more stability. Keep it consistent within a pool.
Who should use this calculator
League organisers, club players, and game designers who want a fair, self-correcting rating system. It works for chess, tennis, table tennis, esports, board games, or any one-on-one (or team-vs-team) contest with wins, losses and draws.
How Elo ratings work
Elo turns a rating difference into a win probability. A 400-point gap means the stronger side is expected to score about 91%. After each game, the winner takes points from the loser; the amount depends on how surprising the result was and on the K-factor. Over many games, ratings converge on each player's true strength and self-correct as form changes.
Setting up a rating pool
- Start everyone near a baseline (commonly 1500) or set provisional ratings.
- Use a higher K for new players so they reach their level quickly, then lower it.
- Apply K consistently across the pool for fairness.
- For teams, rate the team as a unit or average player ratings.
Limitations of this calculator
This computes a single head-to-head update with the basic Elo formula. It doesn't model margin of victory, home advantage, rating floors, or multiplayer/free-for-all formats, and it treats one game at a time. Variants (Glicko, TrueSkill) add uncertainty tracking that plain Elo lacks.
Frequently asked questions
How is a new Elo rating calculated?
New rating = old rating + K × (actual score − expected score). The expected score comes from the rating difference, and the K-factor scales how much one game changes the rating.
What is the K-factor?
It controls volatility: high K (40) for new players who need to find their level quickly, lower K (10–20) for established players whose ratings should be stable.
Why do I gain more for beating a stronger player?
Because the result was less expected. Elo awards points in proportion to how surprising the outcome is, so upsets move ratings more.
Can Elo be used for team sports?
Yes. Rate each team as a single entity, or average player ratings. Many football and esports ranking systems are Elo-based.
What does a 400-point difference mean?
The higher-rated player is expected to score about 91% (roughly a 10-to-1 favorite). Each 400 points represents a tenfold change in expected odds.