ABSTRACT Given the efficiency of the residue number system in high-speed and low-power applications, a wide variety of moduli sets have been introduced in the literature. Selecting an appropriate moduli set is one of the most important issues of using a residue number system. Moduli sets can be evaluated by several factors such as dynamic range, balanced channels, fast and low-power modular operations, and efficient reverse converter. In this paper, 3- and 4-moduli sets are separately reviewed and compared from a different perspective. Furthermore, the most efficient 3- and 4-moduli sets are suggested. A new parameter for average delay comparison is introduced, which shows the delay of every bit in the dynamic range providing a fair comparison of moduli sets with different numbers of moduli. Our comparison showed that either balanced channels or the delay of computations are essential factors for designing an efficient new moduli set.