Single-phase inverters play a crucial role in transferring the power from renewable energy sources such as wind, solar, or even a hydrogen-based fuel cell to the load and/or the electric-power grid. In order to attenuate the high-frequency switching components of the inverter's generated voltage and to minimize the distortion of the injected current at the grid/load side, the LC filter is usually employed. This paper proposes a simple closed-form formula to analytically calculate the required inductance of an LC filter in a single-phase full-bridge inverter controlled with unipolar switching pattern. The derived equations demonstrate that the LC filter inductance value depends on modulation index. Moreover, it proves that the angle at which the maximum peak-to-peak ripple current occurs is not a fixed value, and it varies based on modulation index. Furthermore, the simulation results of a 6.6 kW single-phase inverter are provided for two cases of modulation index to confirm derived closed-form equations.