Correlation Calculator
Calculate the Pearson correlation coefficient between two numeric lists.
How it works
- 1Enter your X values and Y values as comma-separated numbers — both lists must have the same length.
- 2The calculator computes Pearson r = Σ[(xᵢ − x̄)(yᵢ − ȳ)] ÷ √[Σ(xᵢ − x̄)² · Σ(yᵢ − ȳ)²], which always falls in [−1, 1].
- 3r near +1 means a strong positive linear relationship, near −1 a strong negative one, and near 0 little or no linear trend.
Use cases
- Checking whether study hours and exam scores move together in educational data.
- Assessing how closely two financial time series are linearly related.
- Validating sensor readings by confirming two measurements of the same quantity correlate.
Frequently asked questions
What does a Pearson r of 0 mean?
An r of 0 indicates no linear relationship. Non-linear patterns (such as a U-shaped curve) can still exist even when r ≈ 0.
Why does the calculator return — (a dash)?
r is undefined when the two lists have different lengths, when fewer than 2 points are given, or when all values in one list are identical (zero variance).
Does correlation imply causation?
No. A high |r| shows two variables move together linearly, but says nothing about which causes which, or whether a third variable drives both.
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