A method by a terminal in a wireless communication system is provided. Downlink control information including modulation and coding scheme (MCS) information is received from a base station. A number of information bits are identified based on the downlink control information. A transport block size (TBS) is identified based on the number of information bits and a TBS candidate set. The TBS candidate set includes values separated by an interval among a plurality of intervals. Each of the plurality of intervals is a multiple of 8. A first interval between first consecutive values included in the TBS candidate set is larger than a second interval between second consecutive values included in the TBS candidate set. The first consecutive values are greater than or equal to a predetermined value, and the second consecutive values are less than the predetermined value.