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Chess Elo Expected Score Calculator

Expected score E_A from rating difference.

Compute the expected score (probability of winning) for player A against player B from their Elo ratings using E_A = 1 / (1 + 10^((R_B − R_A)/400)).

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

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Results

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

E_A = 1 / (1 + 10^((R_B − R_A) / 400))

In depth

Compute the expected score (probability of winning) for player A against player B from their Elo ratings using E_A = 1 / (1 + 10^((R_B − R_A)/400)).