IP header
Accordingly, every fragment except the last must contain a multiple of 8 bytes of data. It is obvious that Fragment Offset can hold 8192 (2^13) units but the packet can't have 8192 * 8 = 65,536 bytes of data because "Total Length" field of IP header records the total size including the header and data. An IP header is at least 20 bytes long, so the maximum value for "Fragment Offset" is restricted to 8189, which leaves room for 3 bytes in the last fragment.