There is provided mechanisms for transmitting payload in a subframe. A method is performed by a first network device. The method comprises obtaining a transport block size (TBS) value by accessing an array storing a plurality of TBS values. The TBS value is proportional to number of user data symbols in a subframe of a given subframe length. One and the same array is accessed regardless of the given subframe length. The method comprises transmitting a physical channel carrying payload in the subframe to a second network device. The amount of data in the payload is determined by the TBS value.