Advances in computational materials modeling enable efficient and cost-effective assessment of alloy behavior during solidification processes, including welding, casting, and additive manufacturing (AM). The ability to predict microstructural evolution and link it to critical material properties has accelerated targeted alloy design and optimized processing conditions across diverse manufacturing methods. In this study, a solidification cracking (SC) model based on alloy composition and fluid dynamics principles is developed. The proposed approach integrates computational thermodynamics with interdendritic fluid dynamics, building upon established concepts such as the solid/liquid interface and interdendritic fluid pressure drop. Validation of the model was performed through benchmarking against literature data and experimental verification using the Transvarestraint test. Additionally, a new methodology—the Flow Resistance Index (FRI)—is introduced to quantify SC susceptibility in metallic alloys. FRI effectively captures the influence of alloying elements on cracking susceptibility across various metal systems, including aluminum alloys, austenitic stainless steels, and nickel-based alloys. The versatility of the FRI makes it particularly suitable for materials design, alloy selection, and optimization of processing parameters in solidification-based applications such as welding, cladding, additive manufacturing, and traditional casting.