In this paper, the effect of soil material parameters including soil specific weight (γ), cohesion (C), angle of internal friction ( $$\emptyset$$∅ ), and geometric parameter of slope including angle with the horizontal (β) for a constant slope height (H) on factor of safety (F_s) was investigated.F_swas considered in two scenarios: (1) slope with dry condition, and (2) with steady-state saturated condition that comprises water level drawdown circumstances. In addition, the type of slip circle was also investigated. For this purpose, theSLOPE/Wsoftware as a subgroup ofGeo-Studiosoftware was implemented. Results showed that decreasing of water table level and omitting the hydrostatic pressure on the slope consequently would result in safety factor decrement. Comparison of the plane and circular failure surfaces showed that plane failure method produced good results for near-vertical slopes only. Determination of slip type showed that for state (30° < β < 45°), the three types of failure circles (toe, slope or midpoint circle) may occur. For state (45° < β < 60°), two modes of failure may occur: midpoint circle and toe circle. For state (β > 60°), the mode of failure circle is only toe circle. Linear and nonlinear regression equations were obtained for estimation of slope safety factor.