This chapter develops, in readers, the skill of designing a sand casting system to produce defect-free castings. The sand casting design includes: pattern design, gating system design (sprue design, runner design, riser design, etc.), and mold design. Pattern design has been analyzed, taking into consideration machining allowance, shrinkage allowance, and draft allowance with the aid of illustrations and tables. The casting gating system has been explained with reference to recent developments in this technology. Sprue design rules have been listed and elaborated. The taper in sprue design has been mathematically justified with the application of the law of continuity. Sprue design has been analyzed, including the calculation of Reynolds number. Riser design methods have been introduced and the modulus method has been applied to design risers. Mold design has been thoroughly discussed, and numerically analyzed with reference to the use of chaplets for cores, thrust (buoyant force), metallostatic force, and the weight needed to place on the top of cope to prevent its lifting. This chapter contains 22 diagrams, 27 worked numerical examples, 4 tables, 17 equations/formulas, and 6 MCQs with answers.