Correlation Coefficient Calculator

This calculator measures how strongly two variables move together, returning Pearson's correlation coefficient, known as r, and the coefficient of determination, R-squared. Correlation is one of the most used ideas in statistics, telling you whether two things rise and fall together, move in opposite directions, or have no linear relationship at all. Pearson's r runs from minus one to plus one: a value near plus one means a strong positive relationship, where high x goes with high y; near minus one means a strong negative relationship; and near zero means little or no linear association. R-squared, the square of r, tells you the proportion of the variation in one variable that is explained by a straight-line relationship with the other, which is why it is reported alongside regression lines. You paste your x values and your y values into the two boxes, with the same number of points in each, and the calculator returns r, R-squared, the number of pairs, and an interpretation of the strength. The results update as you edit the data. Use it to explore relationships in data, to check a statistics assignment, or to quantify how well two measures track each other, such as study hours and test scores, or temperature and sales. A crucial caution: correlation does not imply causation, and r only captures linear relationships, so a strong curve can show a low r. Always plot your data as well. The calculation uses the standard Pearson formula and is exact for your inputs, rounded for display.

r runs from -1 to +1. Correlation is not causation, and r only measures linear relationships. Use equal-length x and y lists. Rounded for display.