Correlation Coefficient Calculator
Calculate Pearson's correlation coefficient (r) between two paired data sets — how strongly they move together.
Correlation coefficient (r)
—
r² (variance explained) —
Strength —
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How it works
r = Σ((x−x̄)(y−ȳ)) ÷ √(Σ(x−x̄)² × Σ(y−ȳ)²)Frequently Asked Questions
How do I interpret a correlation coefficient?
r ranges from −1 to +1: values near +1 mean strong positive correlation (both rise together), near −1 strong negative (one rises as the other falls), and near 0 means little linear relationship. Above about 0.7 (or below −0.7) is generally considered strong.
Does correlation mean causation?
No — two variables can correlate strongly without either causing the other, often because both are driven by a third factor. Correlation only measures association, never proves cause and effect.
What is r-squared?
The correlation coefficient squared, representing the proportion of variance in one variable explained by the other. An r of 0.8 gives r² = 0.64, meaning 64% of the variation is explained by the linear relationship.