Correlation Calculator
Calculate Pearson’s correlation coefficient, p-value, confidence interval, and a scatter plot from paired observations.
Why use this calculator
Measure how two numeric variables move together
Pearson’s correlation summarizes the direction and strength of a linear relationship between paired values. Paste one value per row or separate values with commas; each value in X must correspond to the value in the same position in Y.
What does Pearson correlation mean?
Pearson’s r ranges from −1 to +1. Positive values mean that higher X values tend to appear with higher Y values; negative values mean the opposite. Values near zero indicate little linear association in the observed data.
The p-value and confidence interval quantify uncertainty, but neither establishes causation. A third variable, selection process, time trend, or outlier can create an association even when changing X would not change Y.
How to interpret a correlation
Inspect the scatter plot first
A single outlier or curved pattern can make r misleading. The chart helps show whether a linear summary is representative of the paired observations.
Pair observations correctly
Both values must come from the same unit and period: for example, one user’s sessions and purchases, or one market’s spend and revenue. Do not correlate independently aggregated lists.
Correlation is not a treatment effect
Use a randomized comparison or an appropriate causal design to estimate impact. Correlation is useful for description, monitoring, and generating hypotheses—not proving that one variable causes another.