Methods and apparatus, including computer program products, are provided for multi-slot transport block size determination. In some example embodiments, there may be provided a method that includes calculating a number of resource elements allocated within a resource element set based at least on an overhead value used for transport block size determination of a transport block that is transmitted over multiple slots; calculating a total number of resource elements, allocated for a physical uplink shared channel or a physical downlink shared channel, covering multiple slots for the transport block size determination based at least on the calculated number of resource elements allocated within the resource element set; and transmitting or receiving the transport block over multiple slots. Related systems, methods, and articles of manufacture are also disclosed.