pjhtech Tools
Link & transport

VLAN / Ethernet Frame Overhead Calculator

Calculate Ethernet frame size, tag cost, padding and payload efficiency.

Input

For IP, enter the whole IP packet including its header. Exclude Ethernet header, tags, padding and FCS.

Reset restores the example inputs.

Local calculation · inputs are not sent to a server.

Result

Calculating the example…

Enter the Ethernet payload length. For an IP packet, include its IP header but leave out the Ethernet header, VLAN tags, FCS and Ethernet padding. Select the tags to add. Ethernet frame including FCS is the complete frame size.

Example: A 1500-byte IP packet with one VLAN tag becomes a 1522-byte Ethernet frame including FCS. Preamble and the gap between frames use additional link time, equivalent to sending 20 more bytes.

The gap consumes time; it is not a field inside the frame. The model adds only enough padding to reach a 64-byte frame with the selected tags. Inserting a tag into a frame that is already padded can retain that older padding and produce a larger frame. LLC/SNAP, MACsec, PHY coding and FEC are not included.

References