🔗Correlation Coefficient Calculator
Enter paired x, y data — one pair per line — to find Pearson's correlation coefficient.
One pair per line, separated by a comma or space. Needs at least 2 pairs.
Free Correlation Coefficient Calculator
This correlation calculator finds Pearson's correlation coefficient (r), which measures the strength and direction of the linear relationship between two variables. Values range from −1 (perfect negative correlation) to +1 (perfect positive correlation), with 0 meaning no linear relationship.
Paste your paired x, y data — one pair per line — and the calculator computes r, the coefficient of determination (r²), a plain-language strength label, and plots the points on a scatter chart so you can visually confirm the trend.
Useful for research, coursework, or quickly checking whether two variables move together. Free, runs entirely in your browser, no sign-up required.
About the Correlation Coefficient Calculator
Features
Pearson's r and r²
Both the coefficient and its interpretation as explained variance.
Strength label
A plain-language read on how strong the relationship is.
Scatter plot
Visualize your data points with a best-fit trend line.
Instant, private
Runs entirely in your browser. No data is sent anywhere.
Frequently Asked Questions
What is Pearson's correlation coefficient?
Pearson's r measures the strength and direction of the linear relationship between two variables, ranging from −1 (perfect negative) to +1 (perfect positive), with 0 meaning no linear relationship.
What does r² mean?
r², the coefficient of determination, is the proportion of variance in one variable that's explained by its linear relationship with the other — an r of 0.8 gives an r² of 0.64, meaning 64% of the variance is explained.
What counts as a strong correlation?
As a rough guide: |r| ≥ 0.9 is very strong, 0.7–0.9 is strong, 0.4–0.7 is moderate, 0.1–0.4 is weak, and below 0.1 is negligible. Context matters — these thresholds vary by field.
Does correlation mean causation?
No. A strong correlation shows two variables move together, but doesn't prove one causes the other — there could be a third factor, reverse causation, or pure coincidence.
What does a negative r mean?
A negative r means the variables move in opposite directions — as one increases, the other tends to decrease.
Why does this only measure linear relationships?
Pearson's r specifically captures linear association. Two variables can have a strong non-linear relationship (like a U-shape) while still showing an r close to 0.
How many data points do I need?
At least 2 pairs are needed mathematically, but meaningful correlations typically need many more — small samples can show misleadingly strong or weak correlations by chance.
What format should I enter data in?
One x, y pair per line, separated by a comma or space, such as '3, 7' or '3 7'.
What does the dashed line on the scatter plot show?
It's the best-fit linear regression line through your data points, shown to visually illustrate the trend that r is measuring.
Is this calculator free to use?
Yes, completely free with no sign-up, and it runs entirely in your browser.