Visual packet size calculator

Visual packet size calculator

Parent interface MTU:
Calculation mode:
Encapsulated protocol MTU (subtract overhead from the parent interface MTU)
Frame size (add overhead to payload size)
Header size (overhead):


Knowing the encapsulation overhead of your protocol stack is important for configuring VPN tunnels. You need to set the tunnel interface MTU correctly, to avoid excessive packet fragmentation.

This tool allows you to easily see what each protocol adds to your packet. Click protocol buttons to add protocols to the stack. Some protocols have additional options, e.g. if you click Ethernet, you will see VLAN and QinQ header option checkboxes.

You can click the same protocol button more than once, e.g. for the IPIP encapsulation you just click the IPv4 button twice.


Header sizes for VXLAN, LISP, and WireGuard include UDP, and STT includes TCP, because these protocols never use any other L4 protocol. Everything else is pure header size, without any outer or inner protocols, e.g. “MPLS” is the size of a single MPLS label (4 bytes).

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