Embodiments of the present disclosure relate to methods, devices and computer readable storage medium for transport block size (TBS) configuration. In example embodiments, a terminal device transmits a random access preamble to a network device. The terminal device receives a random access response from the network device. The random access response includes a resource allocated for a reference TBS. Based on the reference TBS, the terminal device determines a TBS for transmitting data to the network device. Then, the terminal device transmits the data to the network device by using the determined TBS and the allocated resource. This TBS configuration is more flexible.