Elo Rating Change Calculator

Work out elo rating change instantly with clear inputs, formula shown and shareable results.

About Elo Rating Change Calculator

Expected points are the per-game expectancy times games played, and the change is K times actual minus expected; performance rating inverts the Elo curve on the score percentage. Performance rating shows the level you actually played at, independent of your current rating, which is the fairer measure of a single tournament.

Formulas

Expected points

expected = games x 1 / (1 + 10 ^ ((opponent average - rating) / 400))

Performance rating

performance = opponent average - 400 x log10(1 / score fraction - 1)

Worked example

With the default values below, Elo Rating Change Calculator returns Rating change for the event of 35.39. Change any input above and every figure here is recalculated in your browser.

Inputs used

Current ratingminimum 1: 1,720
Average opponent ratingminimum 1: 1,780
Games playedminimum 1: 9
Points scoredminimum 0: 5.5

Results

Rating change for the event: 35.39
Rating after the event: 1,755.4
Points expected: 3.73
Performance rating for the event: 1,859

Step by step

1Values used
2Expected points
3Performance rating
4Rating change for the event= 35.39
5Rating after the event= 1,755.4
6Points expected= 3.73
7Performance rating for the event= 1,859

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Elo Rating Change figure worked out?

expected = games x 1 / (1 + 10 ^ ((opponent average - rating) / 400)). Expected points are the per-game expectancy times games played, and the change is K times actual minus expected; performance rating inverts the Elo curve on the score percentage.

Why does this matter?

Performance rating shows the level you actually played at, independent of your current rating, which is the fairer measure of a single tournament.

What do I need to enter?

Enter current rating, average opponent rating, games played, points scored. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.