We propose a method of volume estimation based on spherical harmonic coefficients of compensated topography. It shows that volume of compensated topography depends merely on sum of coefficients between compensated topography and windowed constant height. The algorithm shows a simplification of computation and improves efficiency of estimation. Moreover, it demonstrates smaller error than general numerical methods. It can be employed in estimating volume of compensated topography windowed with various shapes. This method provides a good reference for estimation of lunar parameters, especially the elastic thickness over mare basins.