Variance inflation factor (${\mathrm{VIF}}_j=(1-R_j^2{)}^{-1}$)

For a slope in a regression with an intercept, the variance inflation factor is $1/(1-R_j^2)$, where $R_j^2$ comes from regressing its predictor on all the others. With one other predictor it is $1/(1-r^2)$, quantifying the increase in conditional estimation variance.