Chess Elo Rating Calculator

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

About Chess Elo Rating Calculator

Elo sets the expected score from the rating difference as 1 / (1 + 10 ^ (difference / 400)), then adjusts by the K factor times the gap between actual and expected results. A 400 point gap implies about a 91% expectation for the favourite, which is why the scale is calibrated in units of 400 rather than arbitrary points.

Formulas

Expected score

E = 1 / (1 + 10 ^ ((opponent - you) / 400))

New rating

new rating = old rating + K x (score - E)

Worked example

With the default values below, Chess Elo Rating Calculator returns New rating of 1,604.1. Change any input above and every figure here is recalculated in your browser.

Inputs used

Your ratingminimum 1: 1,600
Opponent ratingminimum 1: 1,750
Your scoreone of Win (1), Draw (0.5), Loss (0): Draw (0.5)
K factoraccepts 1–40: 20

Results

New rating: 1,604.1
Rating change: 4.07
Expected score: 29.66%
Rating gap: 150

Step by step

1Values used
2Expected score
3New rating
4New rating= 1,604.1
5Rating change= 4.07
6Expected score= 29.66
7Rating gap= 150

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 Chess Elo Rating figure worked out?

E = 1 / (1 + 10 ^ ((opponent - you) / 400)). Elo sets the expected score from the rating difference as 1 / (1 + 10 ^ (difference / 400)), then adjusts by the K factor times the gap between actual and expected results.

Why does this matter?

A 400 point gap implies about a 91% expectation for the favourite, which is why the scale is calibrated in units of 400 rather than arbitrary points.

What do I need to enter?

Enter your rating, opponent rating, your score, k factor. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.