A method, wireless device and network node for supporting sub-physical resource block transmissions over a physical uplink shared channel, PUSCH, are disclosed. According to one aspect, a method includes receiving an indication of a number of resource units to be used for performing sub-PRB transmissions over the PUSCH. The method further includes mapping the number of RUs to a number of physical resource blocks, PRBs and determining a transport block size, TBS, for a sub-PRB transmission over the PUSCH, based on the mapping of the number of RUs to the number of PRBs. The method also includes transmitting sub-PRB transmissions over the PUSCH according to the determined TBS on the number of RUs.