Cantilever retaining walls are earth-retaining structures commonly used in construction. Conventional methods used to determine the active earth thrust acting on a wall often neglect friction between the soil and wall. This study presents an analytical solution for determining the active earth thrusts acting on a cantilever retaining wall with a short heel and a shear key that supports granular backfill. Three different earth thrusts were considered to be acting on three different parts of the rear face of the wall; the thrusts were derived using the limit equilibrium method. The active earth thrust formulas were also simplified in terms of earth thrust coefficients, unit weight, and wall height. An algorithm was developed to obtain earth thrust coefficients depending on various wall dimensions and internal friction angles and to prepare graphs representing earth thrust coefficients and failure surface angles. The effects of wall dimensions and internal friction angles on the earth thrusts and failure surface angles were determined. Finally, the proposed method of determining earth thrust coefficients was compared with other approaches.