Patternmaking plays a crucial role in sand-casting process. This paper discusses the DFM criteria of pattern allowances for a Bush model casting. Here, an algorithm is developed for incorporating all the allowances just by giving input the part model to be casted and the final output from the algorithm is the modified pattern dimension. The calculation of dimensions for the pattern after various allowances like shrinkage, machining and draft is done in a sequential manner. The initial design is done in the modelling software SolidWorks 2016, and then, the allowances are incorporated one by one. Finally, the modified dimension for the pattern is calculated. In this paper, an overall process by which the final dimension of a pattern can be calculated by following a particular sequence of pattern allowances is discussed. The calculation sequence developed may be helpful for various students and casting technicians to find the accurate pattern dimensions.