What does the correlation coefficient mean?

Pearson r ranges from -1 to +1. Values near +1 mean a strong positive linear relationship, near -1 a strong negative one, and near 0 little or no linear relationship.

R-squared is the square of r and represents the proportion of variance in one variable explained by a linear fit to the other. An r of 0.8 gives r-squared of 0.64, or 64%.

Does correlation mean causation?

No. A high correlation only describes how closely two variables move together; it does not prove that one causes the other.

Correlation Calculator

Pearson r for two paired data series.

Correlation calculator

This tool computes the Pearson product-moment correlation coefficient r for two paired data series, measuring the strength and direction of their linear relationship on a scale from −1 to +1. It also reports r² and a plain-English strength reading.

Paste your two series — every value pairs by position, and all calculation happens in your browser.