Correlation coefficient calculator
Enter both variables in matching order, such as study hours and marks, to see how strongly they move together in a straight line.
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How to use it
- Enter x values and y values (same order as x).
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
r = Σ(x - x̄)(y - ȳ) ÷ √(Σ(x - x̄)² × Σ(y - ȳ)²). Significance: t = r√((n - 2) ÷ (1 - r²)) with n - 2 degrees of freedom.
Example
Result: Correlation coefficient (r): 0.774597; Coefficient of determination (r²): 0.6; p-value (two-tailed): 0.124027.
Limits and caveats
- Measures straight-line association only; r can be near zero even when a strong curved pattern exists.
- The strength bands (0.3 and 0.7) are a common rule of thumb, not a fixed standard.
- Correlation does not show that one variable causes the other.
Questions about this tool
What does r between -1 and 1 mean?
1 is a perfect positive line, -1 a perfect negative line and 0 means no linear relationship.
How do I read the p-value?
If p is below 0.05, the correlation is significant at the 5% level, meaning chance alone is an unlikely explanation.
Does it match Excel CORREL?
Yes, r here equals the result of CORREL and PEARSON.