A sand layer overlying clay is common in practice. The conventional Terzaghi's bearing capacity theory is unavailable in this type of nonhomogeneous soil. The semi-empirical methods toward addressing the bearing capacity of strip footings on sand overlying clay, which are widely used in geotechnical engineering, may yield unreliable solutions. In this paper, the bearing capacity of footings on sand overlying clay is evaluated using discontinuity layout optimization (DLO), which is a rigorously upper bound limit analysis method. A bearing capacity reduction factor is developed based on the conventional Terzaghi's bearing capacity theory, and a set of design charts of this factor for various scenarios is illustrated. Subsequently, a simplified regression-based approach, relevant to a wide range of geometric and strength parameters, is proposed. Based on a database of the bearing capacity of footings on sand overlying clay from prior literatures, the model uncertainty for the proposed method is validated and characterized.