Abstract: Plate breakwaters have been identified as a cost-effective solution for wave dissipation infrastructure at the periphery of offshore floating photovoltaic systems. The force characteristics of fixed single-plate breakwaters are analyzed through physical model tests and numerical simulations. The relationship among the maximum vertical force of the plate breakwaters, the relative plate width, relative submergence depth, and relative wave height is examined. Subsequently, simplified formulas are proposed for calculating the dimensionless maximum total pressure and dimensionless maximum total buoyancy force of the plate breakwaters. The results demonstrate that the fitting errors between the formula predictions and the statistical data of double-layer and multi-layer plate breakwaters remain below 10%. This indicates that the simplified formulas can be effectively applied to estimate the maximum vertical forces in fixed plate breakwaters with arbitrary layer configurations.