Calculate Elo changes in seconds.
Use standard Elo expected-score math for one game, match play, or tournament batches. Great for clubs, coaches, school events, and rating experiments.
Formula
R + K × (S − E)
Modes
Single + Batch
Storage
Local History
How Elo works
Expected score estimates your chance against an opponent based on rating difference.
Actual score is 1 for win, 0.5 for draw, and 0 for loss.
K-factor controls how quickly your rating changes. Higher K means bigger swings.
For multi-game events, this app uses the starting rating against every opponent, which is the common simple Elo batch method.
Single Game Calculator
Calculate rating change after one game.
Expected
0.500
Change
+10.0
New Rating
1510
Win Chance
50%
Tournament / Match Calculator
Add multiple opponents and calculate total rating change.
| # | Opponent | Result | Expected | Change | Action |
|---|
Score
0 / 0
Expected
0.00
Change
0.0
New Rating
1500
Estimated performance rating
—
Performance rating is an estimate based on average opponent rating and score percentage.
Target Rating Helper
Estimate what score you need to reach a target rating.
Required score
—
Saved History
Saved only on this device using localStorage.
| Date | Type | Start | Score | Change | New | Action |
|---|
No saved calculations yet.
Notes for official ratings
This tool uses the standard Elo calculation and is useful for planning and estimates. Official chess federations may apply additional rules, rounding methods, rating floors, provisional rating rules, inactivity rules, or event-specific regulations.