Elo Rating Calculator

This Elo Rating Calculator computes new player ratings after a competitive match using the standard Elo system. Enter both players' current ratings, the match result, and the K-factor to see expected scores, rating changes, and updated ratings for both sides.

The Elo Rating Formula

Expected score: E = 1 / (10^((opponent - player) / 400) + 1). Rating change: Δ = K × (actual score - expected score). A win scores 1, a draw 0.5, and a loss 0. When two equally rated players meet (1500 vs 1500), each has a 50% expected score; a win with K=20 gains +10 points.

Understanding the K-Factor

The K-factor controls how much ratings swing per game. Chess often uses K=20 for established players and K=40 for newcomers. Higher K values make ratings more volatile; lower K values stabilize rankings over many games.

Frequently Asked Questions

How is Elo rating calculated after a match?

Calculate the expected score from the rating difference, then multiply the K-factor by the difference between the actual result (1, 0.5, or 0) and the expected score. Add that change to the player's rating.

What is a good starting Elo rating?

Most systems start new players at 1200-1500. Chess platforms commonly use 1500 as the default starting rating for unrated players.

What does the K-factor mean in Elo?

K determines rating sensitivity per game. K=20 is standard for experienced players; higher values (30-40) are used for beginners so ratings converge faster to true skill.

Can I beat a higher-rated player and gain more points?

Yes. Upsets yield larger gains because the expected score is low. Beating a much higher-rated opponent produces a bigger positive change than beating someone at your level.

Is Elo only used in chess?

No. Elo-style ratings are used in many sports and games including table tennis, esports, soccer rankings, and competitive board games. The same math applies wherever relative skill is measured.

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Elo Rating