The disclosure pertains to selecting a Transport Block Size (TBS) in a communication system. An aspect is directed to an apparatus for selecting a Transport Block Size (TBS) for a transmitter of a communication system. The communication system supports variable Transmission Time Interval (TTI) lengths regarding the number of symbols to be transmitted in one TTI. The apparatus is configured to receive first information indicative of a TTI length, receive second information indicative of a number of reference symbols included in the TTI, decode, from the first information, the TTI length, and decode, from the second information, the number of reference symbols included in the TTI. The apparatus is further configured to calculate, based on the TTI length and based on the number of reference symbols included in the TTI, a number of data symbols included in the TTI, calculate, based on an allocation bandwidth and based on the number of data symbols included in the TTI, a number of data Resource Elements (REs) in the TTI, and select the TBS from a data structure, based on the calculated number of data REs. Further aspects of the disclosure pertain to a base station, a UE, methods, computer programs, computer-readable recording media and a system.