Calculate total Ethernet frame size including headers, payload and trailer.
The total Ethernet frame size on the wire is the payload plus a 14-byte header (destination/source MAC and EtherType) and a 4-byte Frame Check Sequence; a tagged trunk frame adds a further 4-byte 802.1Q VLAN tag between the source MAC and EtherType fields. Ethernet also enforces a 64-byte minimum frame size, so undersized payloads are padded up to that floor, and any frame exceeding 1518 bytes (1522 with a VLAN tag) is considered oversized unless the network explicitly supports jumbo frames.
Total frame size
total = payload + ethernet_header(14) + FCS(4) [+ VLAN_tag(4) if tagged]
The standard maximum is 1518 bytes total (1500-byte MTU payload + 14-byte header + 4-byte FCS). An 802.1Q VLAN-tagged frame adds 4 more bytes, raising the tagged maximum to 1522 bytes. Anything larger requires jumbo frame support end-to-end.
The minimum frame size exists so that, historically on shared half-duplex Ethernet (CSMA/CD), a transmitting station could reliably detect a collision before finishing sending a frame — a frame shorter than the round-trip propagation delay of the segment could complete transmission before a collision was noticed. Modern full-duplex switched networks don't need this for collision detection, but the minimum remains part of the standard, and undersized frames are padded to meet it.
An 802.1Q tag adds exactly 4 bytes to every frame that carries it (2 bytes Tag Protocol Identifier + 2 bytes Tag Control Information containing the VLAN ID and priority bits), which is why the maximum tagged frame size is 1522 rather than 1518 bytes.