Correlation Coefficient Calculator

x values — commas or spaces

y values — same count as x

Correlation r —

r² (determination) —

Pairs (n) —

Strength —

How to Calculate the Correlation Coefficient

Enter two equal-length lists of paired values.

Enter paired data

Type your x values in one box and the matching y values in the other. Each x must have a y, so the two lists have the same length.

Read the coefficient r

r ranges from −1 to +1. Positive means the two rise together, negative means one rises as the other falls, and near 0 means little linear relationship.

Check r² and strength

r² is the share of variance explained, and the strength label summarises how strong the relationship is.

Frequently Asked Questions

What does the correlation coefficient tell you?

Pearson r measures the strength and direction of the straight-line relationship between two variables, on a scale from −1 to +1. A value of +1 is a perfect positive line, −1 a perfect negative line, and 0 no linear relationship at all. The sign comes from the direction of the trend and the magnitude from how tightly the points hug that line. It only detects linear association, so a strong curved pattern can still give an r near 0.

What is a strong correlation?

As a rough guide, an absolute r above about 0.7 counts as strong, 0.4 to 0.7 as moderate, and below 0.2 as very weak. These thresholds are conventions rather than rules: in physics an r of 0.9 may be disappointing, while in social science 0.4 can be a notable result. Sample size matters too, because a small sample can produce a large r by chance alone. A high correlation never establishes causation on its own.

What is r-squared?

The coefficient of determination r² is simply the correlation squared. It is the proportion of the variation in one variable explained by a linear fit on the other, so r = 0.8 gives r² = 0.64, or 64%. Because squaring removes the sign, r = −0.8 gives the same r² of 0.64. Halving r quarters r², so an r of 0.4 explains only 16% of the variation.

Is my data sent anywhere?

Your figures stay on your device when you use the correlation coefficient calculator. The correlation coefficient calculator works in the browser using JavaScript, with no server round-trip at any point, so both data columns are never transmitted. Nothing is logged, stored or shared with a third party. That also means the tool keeps working offline.

How to Calculate the Correlation Coefficient

Enter paired data

Read the coefficient r

Check r² and strength

Frequently Asked Questions

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