. Shallow foundation used to support relative small buildings for examples house foundation and ordinary multistoried building. Relative density (Dr) usually indicate density level of granul soil in the field. In the Terzaghi's bearing capacity formula for shallow foundation (1943), relative density (Dr) was represented by value of angle of internal friction (φ) which is used as a basic to determine a value bearing capacity factor and was applyed on every types of soil. To investigate the effects of relative density to the bearing capacity formula of shallow foundation on sand under centric load, study has been performed at the Geotechnical Laboratory Muhammadiyah Mataram University and Structure Laboratory Mataram University. Procedure of the research is: foundations was made from rigid iron plate with dimensions of 20x20cm, 30x30cm, 40x40cm, 20x30cm, 20x40cm, and 30x40cm, and sand media with various relative density of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% was laid on box testing and applied with centric loads. Test was stopped when the foundation ruptured. Results obtained from this research show that the relative density (Dr) determine the ultimate bearing capacity shallow foundation, the greater relative density of sand greater the ultimate bearing capacity of foundation.