The recently-completed PISA (PIle Soil Analysis) research project aimed to improve the design of monopile foundations for offshore wind turbines (OWT), focusing on laterally-loaded monopiles with length-to-diameter (L/D) ratios between 2 and 6. The project resulted in a novel one-dimensional (1D) design model which overcomes certain limitations in current practice. The PISA 1D design model facilitates rapid design calculations, based on the use of Timoshenko beam theory to represent the monopile. The soil response is modelled via soil reactions, applied along the shaft and at the base of the monopile. The soil reaction curves are determined using a series of three-dimensional (3D) finite element (FE) calibration calculations, performed prior to the design process, spanning a representative design space. A new software tool called PLAXIS MoDeTo (Monopile Design Tool) has been developed based on this design procedure. This design tool facilitates the automatic generation and calculation of the 3D FE calibration models, the optimisation of the soil reaction curves and the conduct of the 1D design calculations.