About MTU Calculator

Calculate the maximum payload that fits within a given MTU after subtracting protocol header overhead. Select from 11 protocol headers across Layer 2 through tunneling and security protocols—Ethernet (14B), IPv4 (20B), IPv6 (40B), TCP (20B), UDP (8B), PPPoE (8B), GRE, IPSec ESP, MPLS, VLAN 802.1Q, and L2TP. The tool computes remaining payload, protocol efficiency percentage, fragmentation risk, and context-aware recommendations.

• Eight preset MTU sizes from 296 (point-to-point) through 9000 (jumbo frames)
• Variable-size headers (IPv4 20–60B, TCP 20–60B, GRE 4–16B, IPSec ESP 8–50B) noted in the UI
• Warns when both IPv4 and IPv6 headers are selected simultaneously
• Flags payloads below the 576-byte minimum safe Internet MTU
• Recommends MTU 1492 for PPPoE connections on standard 1500-byte Ethernet
• Export a full analysis report as text file with protocol stack breakdown

Frequently Asked Questions

When should I use jumbo frames (MTU 9000)?

Only on local networks where every hop supports them—typically storage area networks, hypervisor clusters, or dedicated backup LANs. Jumbo frames on the public Internet will get fragmented or dropped.

Why does my PPPoE connection need a smaller MTU?

PPPoE adds an 8-byte header inside the Ethernet frame. At the standard 1500-byte Ethernet MTU, that leaves only 1492 bytes for the IP packet. If your MTU stays at 1500, packets will fragment or fail silently.