Elo Rating Calculator

Your rating

Opponent rating

K-factor

Forty for beginners, 20–32 for ordinary players, ten for masters.

Result

New rating1,520.5
Change20.5
Expected result, %35.99%
If you win1,520.5
If you lose1,488.5
Rating gap100

The reward depends on the opponent

Works out how a rating moves after a game, from the gap in strength and the K-factor.

The Elo system rests on one idea: the rating gap predicts the chance of winning. Two hundred points means roughly a 76 percent chance, four hundred about 91. A player gains or loses in proportion to how far the result diverges from that expectation.

The K-factor sets how fast a rating moves. It is high for beginners — the system is still searching for their true level. It is low for grandmasters: their strength is known, and one game should not re-evaluate it.

What this calculator shows

The new rating and the size of the change
The expected result of the game as a percentage
What a win and a loss would each do

What to keep in mind

The classic Elo formula is used, base 10 with a divisor of 400 — the one chess adopted.
Many games apply their own modifications: hidden ratings, score adjustments, demotion protection. The exact rules vary.

FAQs

How does the Elo formula work?

The expected result comes from the rating gap on a logistic curve, and the change equals the K-factor times the difference between actual and expected results.

What is the K-factor?

The maximum rating change per game. Forty for beginners, twenty to thirty-two for ordinary players, ten for the strongest.

Why is beating a weak player worth so little?

Because it was expected. If the system puts your chances at 90 percent, a win confirms what it already knew and barely moves the estimate.

What does a 200-point gap mean?

The stronger player is expected to score about 76 percent. At K = 32 a win earns them roughly 7.7 points and a loss costs 24.3.

Worked example

Beating a stronger player

Input: Your rating 1500, opponent 1600, K = 32, a win

Output: Plus 20.5 points, taking the rating to 1520.5

Note: The expected result here is only 36 percent, so the win pays more than half the K-factor. Losing to the same opponent would have cost just 11.5 points.

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