The need for efficient and sustainable strengthening methods has led to increased interest in advanced fiber-reinforced polymer (FRP) composites in structural engineering. This study focuses on the performance optimization of Basalt Fiber Reinforced Polymer (BFRP) sheets in retrofitting reinforced concrete (RC) beams. The primary objective is to develop a generalized predictive equation to estimate the modulus of elasticity of BFRP sheets as a function of their thickness, eliminating the reliance on extensive physical testing. To achieve this, a comprehensive parametric analysis was performed using finite element modeling (FEM) in ABAQUS. The numerical models were validated against experimental data under both three-point and four-point loading conditions. Continuum shell elements were used to represent the BFRP layers, and cohesive interaction was defined at the concrete–BFRP interface. The mechanical properties of the BFRP layers were derived from regression analysis of existing experimental datasets, resulting in a scalable equation that correlates thickness with elastic modulus. Simulation results showed strong agreement with experimental findings, with a maximum deviation of less than 10% from experimental results, indicating high reliability. Increasing the BFRP thickness from 0.12 to 0.45 mm demonstrated a corresponding decrease in modulus of elasticity by up to 25%, validating the inverse relationship. The formulated equation was found to be scalable with an increasing number of BFRP layers, confirming its robustness and applicability across various reinforcement configurations. These findings provide a computationally efficient approach for predicting the mechanical behaviour of BFRP-laminated RC elements, facilitating the optimized design of high-performance structurally retrofitted systems.