Comminution is the most energy-intensive stage of mineral processing and plays a decisive role in plant performance, equipment selection, and operating costs. Consequently, the preliminary design of crushing circuits requires reliable engineering calculations and systematic evaluation of ore characteristics and design criteria. This paper presents the modernization and verification of the C&G Circuit Designer, a computer-aided engineering application developed to generate preliminary crushing circuits based on established comminution design principles. The application integrates particle size distribution analysis, distribution coefficient estimation, equipment selection, reduction ratio evaluation, and stage-wise mass balance calculations within a unified engineering framework, using the Gaudin–Schuhmann particle size distribution model. Verification against an independently prepared reference design showed close agreement in the predicted distribution coefficient, generated crushing circuit, and stage-wise mass balance, confirming the correct implementation of the stated equations; broader validation against industrial plant data or established commercial simulators is identified as necessary future work. Unlike conventional comminution software, which generally requires engineers to define a process flowsheet before analysis, the developed application generates preliminary crushing circuits directly from ore properties and engineering design criteria, providing a consistent basis for subsequent engineering evaluation and detailed plant design. The modular software architecture supports future expansion through additional equipment databases, closed-circuit finishing stages, and optimization modules while preserving the established design methodology.