The tubesheet is probably the most important part of a heat exchanger since it provides a rigid support to all the tubes and keeps the shell and tube side fluids separated. It has to withstand the pressure, temperature and corrosive nature of both fluids as well as any surges in operating conditions due to upset or emergency conditions. Hence, its design calls for the utmost caution. Since heat exchangers are used in widely varying conditions of pressure, temperature and flow rates, and handle numerous kinds of fluids, no one tubesheet design will suit all situations. Therefore, different designs exist for different situations. This paper presents a comprehensive computer program which calculates the tubesheet thickness for all eleven TEMA (Standards of Tubular Exchanger Manufacturers Association) cases and can be used to design tubesheets for various conditions.