Resultant force caused by the pressure loading of a liquid acting on submerged surfaces are known as Hydraulic force. Calculating the hydrostatic force is necessary to design a building that can resist forces due to its fluid. There are 2 conditions of the submerged surface, those are fully submerged and partly submerged. In this study, three scenarios will be used for developing computer-based program for calculating hydrostatic force and will be compared to manual calculation. The numerical analysis will be conducted using GNU Octave, version 6.2.0. The scenarios are fully submerged plane with 90°, fully submerged plane with inclination angle and partially submerged plane with inclination angle. Overall, from scenario one to three, the percentage differences are 0%, with the mean percentage difference of the program is 0%. Hence, it satisfies all the elements that need to be checked based on the hydrostatic force calculation in Fluid Mechanics.