This paper presents a new algorithm for exact estimation of the minimum memory size required by programs dealing with array computations. Memory size is an important factor a ecting area and power cost of memory units. For programs dealing mostly with array computations, memory cost is a dominant factor in the overall system cost. Thus, exact estimation of memory size required by a program is necessary to provide quantitative information for making high-level design decisions. Based on formulated live variables analysis, our algorithm transforms the minimum memory size estimation into an equivalent problem: integer point counting for intersection union of mappings of parameterized polytopes. Then, a heuristics was proposed to solve the counting problem. Experimental results show that the algorithm achieves the exactness traditionally associated with totally-unrolling loops while exploiting the reduced computation complexity by preserving original loop structure.