Coefficient of Determination (R²) Calculator

About this calculator

The coefficient of determination, R², is simply the square of the Pearson correlation coefficient r, but squaring it changes its meaning in an important way: r tells you the strength and direction of a linear relationship, while R² tells you the percentage of variance in the outcome variable that is explained by the predictor. An r of 0.7 sounds strong, but R² = 0.49 reveals that only 49% of the variation is actually accounted for by the model — the rest is noise or other factors.

Statisticians and researchers report R² alongside every simple linear regression to communicate model fit in a way non-technical readers can grasp as a percentage. Financial analysts use it to measure how closely a stock or fund’s returns track a benchmark index (a high R² means the fund’s performance is largely explained by the market, useful for spotting closet-indexing), and data scientists use it as a baseline metric when evaluating whether a regression model is worth deploying.

Enter your correlation coefficient r, and this calculator squares it to give you R² and the equivalent explained-variance percentage.