Network MTU Calculator

v1.2.1

Compute effective payload sizes for MTU values and encapsulation overhead.

Computes effective payload sizes for MTU values across encapsulation layers (Ethernet, IP, TCP, UDP, VLAN, IPSec, GRE) — useful for diagnosing fragmentation and tuning tunnel configurations.

How to use

→Enter your link MTU (e.g. 1500 for Ethernet) and select the encapsulation stack.
→The effective payload size at each layer is shown with header overhead breakdown.
→Adjust to find the correct MSS or PMTU for your tunnel or VPN configuration.

MTU Size (bytes)

Protocol Overhead

Select protocol overheads and click Calculate to see MTU breakdown.