The coefficient of determination (r2) is a measure of the proportion of variance of a predicted outcome. with a value of 0 to 1, the coefficient of determination is calculated as the square of the correlation coefficient (r) between the sample and predicted data. the coefficient of determination shows how well a regression model fits the data. its value represents the percentage of variation that can be explained by the regression equation. a value of 1 means every point on the regression line fits the data; a value of 0.5 means only half of the variation is explained by the regression. the coefficient of determination is also commonly used to show how accurately a regression model can predict future outcomes.