In this paper, a modified backward/forward sweep (BFS) load flow algorithm is proposed to solve power flow for islanded droop-controlled ac microgrids. The proposed method has been formulated such that the system frequency is one of the system's unknown variables which is typical for an islanded network justifying further the absence of a slack bus. As a result, new equations have been systematically developed and incorporated with the conventional BFS method. The modified BFS method has been applied to the 33-bus test system and the results obtained are compared with simulation results from the direct BFS method as well as PSCAD/EMTDC. In comparison to the conventional methods, the proposed method is accurate, simple, and easy to implement thus serving as a useful tool for microgrid analysis and planning.