Online Tool Store
Correlation Calculator
Calculate Pearson correlation, covariance, means, and an easy-to-read interpretation from two paired numeric datasets in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Pearson correlation coefficient
- Pairs
- 6
- R²
- 0.889
- Mean X
- 3.500
- Mean Y
- 4.833
- Sample covariance
- 4.100
- Direction
- Positive linear relationship
How to calculate correlation
- Enter paired X and Y observations in matching order.
- Select Calculate correlation to validate the lists and compute the results.
- Read Pearson r for direction and strength, then review R², means, and sample covariance.
Pearson r method
The calculator subtracts each series mean, sums the paired deviation products, and divides by the square root of the two deviation sums of squares. Pearson correlation describes linear association only and should be interpreted alongside the data context and a scatter plot.
FAQ
What does Pearson correlation measure?
Pearson r measures the direction and strength of a linear relationship between two numeric variables, from −1 to +1.
What does R² mean here?
R² is the square of Pearson r. It describes the share of variation associated with the fitted linear relationship, but does not establish causation.
Can correlation prove causation?
No. A strong correlation can arise from confounding factors, coincidence, selection effects, or a relationship in the opposite causal direction.
Why must both lists have the same length?
Each X value must be paired with one Y value from the same observation.
What happens with a constant series?
Correlation is undefined when either series has zero variance, because its standard deviation is zero.
What is the minimum number of pairs needed?
At least two paired X/Y values are required to compute a correlation - fewer than that and the calculator flags the input as invalid.
How we compare
| Feature | Online Tool Store | DATAtab | Social Science Statistics |
|---|---|---|---|
| Pearson r | Included | Included | Included |
| R² and covariance summary | Included | Broader statistics suite | Detailed Pearson output |
| Spearman and Kendall methods | Not included | Included | Separate calculators |
| Focused paired-list interface | Included | Dataset workspace | Included |
Choose DATAtab for a broader statistical workflow or Social Science Statistics for significance testing and expanded calculation detail. Choose Online Tool Store Correlation Calculator for a quick local Pearson r, R², covariance, and means summary.