For the design of unreinforced masonry walls under lateral earth pressure according to DIN EN 1996-3 [1], the active earth pressure is used, which is less than the earth pressure at rest. For the consideration of active earth pressure, a sufficient deflection of the wall is needed. It is unknown whether the deflections in reality are large enough to justify a reduction of the active earth pressure. Therefore a numerical model has been developed which considers the load-bearing behaviour of masonry walls, with several boundary conditions being considered to estimate the effective earth pressure.