Correlation Coefficient Calculator
Enter two comma-separated lists of numbers to find the Pearson correlation coefficient (r) between them.
Enter comma-separated numbers. Both lists must have the same number of values.
How the correlation coefficient works
The Pearson correlation coefficient (r) measures the strength and direction of a linear relationship between two variables. It ranges from -1 (perfect negative correlation) to +1 (perfect positive correlation), with 0 meaning no linear relationship.
It's calculated by dividing the covariance of the two variables by the product of their standard deviations — essentially measuring how consistently the two variables move together relative to their own individual variation.
Frequently asked questions
What does an r value of 0.77 mean?
A value around 0.7–0.9 generally indicates a strong positive correlation — as one variable increases, the other tends to increase as well, fairly consistently, though not perfectly.
Does a high correlation mean one variable causes the other?
No — correlation measures how two variables move together, not whether one causes the other. A strong correlation can arise from a third factor influencing both variables, from coincidence in a small sample, or from genuine causation; correlation alone can't distinguish between these.
Can correlation detect any kind of relationship between variables?
No — Pearson's r specifically measures *linear* relationships. Two variables can have a strong non-linear relationship (like a U-shape) and still produce a Pearson r close to zero, since it only captures the straight-line component of their association.