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Correlation Calculator

Enter two lists of paired values to find the Pearson correlation coefficient.

One number per pair, separated by commas or spaces.

Same count as the X values, in the same order.

This result is an estimate only. Double-check important figures before relying on them.

How it is calculated

  • r = Σ(x − x̄)(y − ȳ) ÷ √(Σ(x − x̄)² × Σ(y − ȳ)²)
  • r² is r multiplied by itself

To get the line itself, use the linear regression calculator.

Worked example

X = 1, 2, 3, 4, 5 and Y = 2, 4, 5, 4, 5:

  • r = 6 ÷ √(10 × 6) = 0.7746
  • r² = 0.60

Why your number may differ

Pearson r only measures straight-line relationships and is sensitive to outliers. A curved pattern can give an r near 0 even when the link is strong.

Frequently asked questions

What does r mean?

It runs from −1 to +1. Near +1 the two lists rise together, near −1 one rises as the other falls, and near 0 there is little straight-line relationship.

What is r²?

The share of the variation in Y that a straight line on X explains. An r² of 0.6 means 60%.

Does correlation prove cause?

No. Two things can move together because of a third factor or by chance.

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