Elo Rating Calculator
Elo Rating & Matchup Studio
Rating change dashboard
Expected score share
Includes draw outcomes · not a win probability.
Rating change indicator
1500 → 1520.5 · +20.5
Unrounded: 1520.48208 · Δ +20.48208
Explore the matchup
Compare the upside of a win, draw or loss.
Same starting rating · K = 32
Change the opponent rating or choose a result to update your matchup.
How opponent strength changes your expected score
Classical Elo · 400-point logistic curve
Your rating 1500 vs opponent 1600: +100 opponent rating difference → 36.0% expected score. Equal ratings → 50%.
Change either rating or use the Opponent strength slider above. The blue point follows your matchup. Expected score includes draws; it is not a separate win probability. K and match outcome change rating updates, not this curve.
Set the matchupEnter your rating, opponent rating and settings.
Choose the resultSelect win, draw or loss to see the change.
See the rating changeView new rating, expected score and comparison.
Formula & worked example
Expected score:
New rating: R′ = R + K × (S − E)
1500 + 32 × (1 − 0.359935) = 1520.48208
Display values are rounded; calculations use full precision. S = 1 for a win, 0.5 for a draw, 0 for a loss. The comparison line shows the transition between two values, not a universal rating scale.
FAQ
Is expected score the win probability?
No. In games allowing draws, expected score equals P(win) + 0.5 × P(draw). Elo alone does not identify separate win, draw and loss probabilities. The two shares displayed add to 100% but are not a win-probability forecast.
Which K-factor should I choose?
K controls responsiveness. Classical Elo permits your chosen K. FIDE Standard uses prescribed base K values of 10, 20 or 40 based on rating history, experience and age, then may reduce K for the total number of games in a rating period. Open the guide and consult your player record.
Does this reproduce official FIDE ratings?
FIDE mode uses the Standard PD table and the rating-difference rule effective 1 October 2025 for one rated player. It estimates a single-game contribution using your selected base K and period game count. Official updates sum the whole period before rounding and depend on eligibility and submitted results. Initial ratings, floors, Rapid/Blitz and event processing are outside this tool.
Can I use this for esports?
Use Classical Elo for a custom league with its own consistent rating scale and K. Selecting Esports does not reproduce League of Legends, Counter-Strike or another platform’s proprietary matchmaking or rank system.
What does the live expected-score curve show?
The horizontal axis is opponent rating minus your rating. The vertical axis is expected score. Equal ratings give 50%; a stronger opponent lowers your expected score. The blue point follows your inputs. Classical Elo produces a smooth logistic curve; FIDE mode uses a stepped PD table with the applicable difference cap. K and the chosen result affect your rating change, not expected score.
Why are opponent shares labelled differently in FIDE mode?
The second share is the complement of your expected score. With asymmetric FIDE rating-difference treatment, the opponent’s own rating calculation may use a different capped difference. This tool calculates only your contribution.
Sources & References
FIDE Rating RegulationsRating tables & development factors
US ChessRating-system methodologyFIDE HandbookOfficial rules & rating contextEducational references · no institutional endorsement. Classical Elo and official rating systems differ. Sources checked 19 October 2026.
Explore expected score, potential rating changes and match outcomes with Classical Elo or FIDE rated-player tables.