This paper present 18 regression equations for the computation of optimum gas tank capacity for a wide range of gas carrier vessels. This presentation is to ensure that the optimum total gas carrying capacity of a projected or existing gas carrier vessel with known principal dimensions is adequately computed. The method is authenticated by comparing the tank capacities it predicts, with that of 15 randomly selected existing gas carrier ships. The method presented is important to assure that a projected design of this type of ship meet owner’s requirement regarding total gas tank capacity, to provide for optimization in ship design and to assist in ship design software development