This paper presents a new gravity inversion tool GRV_D_inv, specifically a GUI-based Matlab code developed to determine the three-dimensional depth structure of a density interface. The algorithm used performs iteratively in the frequency-domain based on a relationship between the Fourier transforms of the gravity data and the sum of the Fourier transforms of the powers of the depth to the interface. In this context, the proposed code is time-efficient in computations, and thus, it is capable of handling large arrays of data. The GUI-enabled interactive control functions of the code enable the user with easy control in setting the parameters for the inversion strategy prior the operation, and allow optional choice for displaying and recording of the outputs data without requiring coding expertise. We validated the code by applying it to both noise-free and noisy synthetic gravity data produced by a density interface; we obtained good correlation between the calculated ones and the actual relief even in the presence of noise. We also applied the code to a real gravity data from Brittany (France) for determining the 3D Moho interface as a practical example. The recovered depths from the code compare well with the published Moho structures of this study area.