Calculate Elo expected score and rating movement for any rating gap and K-factor.
How this calculator arrives at its answer
The Elo system converts a rating gap into an expected score. Every 400 points of advantage means the stronger player is expected to score ten times as often as the weaker one, and rating changes are simply the difference between the result and that expectation.
The K-factor sets how fast ratings move. New players use a high K so their rating finds its level quickly; established masters use a low one so a single result does not swing them far.
Try it with these numbers
Worked through, a games in a series of 1 produces a new rating of 1,514. Underneath, Expected score comes out at 29.66% and Rating change at +14.1. Change any field and every figure updates as you type.
Using the calculator
- Enter your rating and your opponent’s.
- Choose the K-factor your federation or site uses.
- Pick the result to see the rating change.
Formula reference
expected score E = 1 ÷ (1 + 10^((opponent − you) ÷ 400))
new rating = old rating + K × (actual score − expected score)
Questions people ask about this
What is a K-factor?
A multiplier controlling how much a single game moves your rating. FIDE uses 40 for new players, 20 for most, and 10 above 2400.
Why does a draw sometimes lose me points?
Because if you were expected to score more than half against a weaker opponent, a draw is a worse result than expected.
Does beating a much weaker player help?
Barely. If you were expected to score 0.97, winning gains you only three percent of the K-factor.