Correlation Coefficient Calculator
Compute Pearson’s r between two lists of numbers.
Results update as you type.
About this calculator
Pearson’s correlation coefficient (r) measures the strength and direction of the linear relationship between two variables, ranging from −1 (perfect negative) through 0 (no linear relationship) to +1 (perfect positive). Enter paired x and y values in the same order; the calculator returns r, the coefficient of determination r² and a plain-English reading of the strength. The two lists must have the same number of values.
Frequently asked questions
What does the correlation coefficient tell me?
It quantifies how closely two variables move together in a straight line. Values near +1 or −1 indicate a strong linear relationship, while values near 0 mean little or no linear association. The sign shows the direction of the relationship.
Does correlation mean causation?
No. A high correlation shows two variables move together but not that one causes the other. A hidden third factor, or pure coincidence, can create a strong correlation with no causal link.
What is R²?
R² is the square of the correlation coefficient. It is the proportion of the variation in y explained by a linear relationship with x — an r of 0.8 gives an R² of 0.64, meaning 64% of the variation is accounted for.
Results are estimates for general guidance only, not financial, medical or tax advice.