Steps can improve the hydrodynamic performance of planing boats in both calm and rough conditions. While transverse steps have been widely studied, the influence of swept (V-shaped) steps remains less understood. This paper presents a mathematical model to predict the calm-water performance of a hard-chine planing boat equipped with forward-swept steps. The method is based on the 2D+T approach and uses a linear wake assumption to estimate the ventilation length behind each step. Model predictions are validated against experimental measurements and CFD results. The validated model is then applied to assess the hydrodynamic performance of swept-stepped hulls in early-stage design and to support designers in optimizing step height, sweep angle, and longitudinal position for improved trim, reduced resistance, and enhanced overall performance. The study extends and validates the 2D+T method for forward-swept configurations, offering a fast and practical tool for concept evaluation, while CFD remains essential for final design refinement.