This calculator will tell you the observed power for a one-tailed or two-tailed t-test study, given the observed probability level, the observed effect size, and the total sample size.

This calculator will tell you the observed power for a hierarchical regression analysis; i.e., the observed power for a significance test of the addition of a set of independent variables B to the hierarchical model, over and above another set of independent variables A. The value returned by the calculator is the observed power for the addition of the set of independent variables B to the overall hierarchical model.

This calculator will tell you the observed power for your multiple regression study, given the observed probability level, the number of predictors, the observed R², and the sample size.