A simple, clean, and responsive web application for calculating chess ELO rating changes based on a series of games. This tool is perfect for chess players who want to track their performance and estimate their new rating after a tournament or a series of matches.
The app is a fully offline-capable Progressive Web App (PWA), built with Vue.js and Vite.
- Cumulative ELO Calculation: Each game's result affects the rating for the next game in the series.
- Dynamic K-Factor: Easily switch between different K-factors (10, 15, 20, 25, 30, 40).
- Performance Statistics: Automatically calculates your performance rating, total points, and average opponent rating.
- Drag & Drop Reordering: Intuitively reorder games to see how the sequence affects the outcome.
- PWA & Offline Support: Installable on any device and works without an internet connection.
- Auto-Save: Your data is automatically saved to your browser's local storage.~~
The calculator uses the official FIDE rating system formulas.
The expected score is the probability of a player winning against their opponent. It is calculated as follows:
E = 1 / (1 + 10^((Ro - Rp) / 400))
E: Expected scoreRo: Opponent's ratingRp: Player's current rating
The new rating is calculated after each game based on the K-factor, the actual score, and the expected score:
R' = Rp + K * (S - E)
R': New ratingRp: Player's current ratingK: K-factor (development coefficient)S: Actual score (1 for a win, 0.5 for a draw, 0 for a loss)E: Expected score
The application calculates these changes cumulatively, meaning the New Rating from one game becomes the Player's current rating for the next game in the list.