R-Squared Calculator
Compute R², the share of variation in y explained by the best-fit line.
What is R-Squared?
R², the coefficient of determination, is the fraction of the variation in y that the fitted line accounts for: 1 − SS_res ÷ SS_tot. It is the square of the correlation for a simple linear fit, so a correlation of 0.5 corresponds to an R² of just 0.25.
How it works
The sums of squared residuals and of squared deviations from the mean both come out of the single least-squares pass, and R² is their complement. The correlation is shown beside it because R² alone hides the direction of the relationship, and the percentage phrasing is included to stop the number being read as a proportion of the correlation.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
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