MTU Calculator

Calculate Maximum Transmission Unit with protocol overhead analysis

Enter the base MTU in bytes, typically 1500 for Ethernet

IP Version

Transport Protocol

Layer 2 Overhead

Tunnel / VPN Overhead

Quick Presets

Enter the physical layer MTU

Select Protocol Layers (in order of encapsulation)

Enter the MTU value you want to test
Enter a hostname or IP address to test path MTU against

IP Version

MTU Reference

Common MTU Values

Network Type MTU Use Case
Ethernet Standard 1500 Default for most networks
PPPoE/DSL 1492 DSL/fiber with PPPoE (8-byte overhead)
IPv4 Minimum 576 Minimum guaranteed non-fragmented
IPv6 Minimum 1280 Minimum required for IPv6
Ethernet Jumbo 9000 High-performance LANs/datacenter
VPN Typical 1400 Common safe value for VPN tunnels

MTU vs MSS

MTU (Maximum Transmission Unit) is the maximum packet size including all headers at Layer 3 and above.

MSS (Maximum Segment Size) is the maximum TCP payload only, calculated as: MTU - IP header - TCP header.

Example: With 1500 MTU and IPv4/TCP: MSS = 1500 - 20 (IPv4) - 20 (TCP) = 1460 bytes

Protocol Header Sizes

Protocol Header Size Notes
IPv4 20 bytes Without options (up to 60 with options)
IPv6 40 bytes Fixed header size
TCP 20 bytes Without options (up to 60 with options)
UDP 8 bytes Fixed header size
ICMP 8 bytes Echo request/reply
GRE 24 bytes 4 GRE + 20 inner IP header
PPPoE 8 bytes 6 PPPoE + 2 PPP
VLAN 802.1Q 4 bytes Single VLAN tag

VPN/Tunnel Overhead

VPN Type Overhead Components
IPsec ESP Tunnel ~73 bytes Outer IP (20) + ESP header (8) + IV (16) + trailer (2) + padding (~15) + ICV (12)
IPsec ESP Transport ~53 bytes ESP header (8) + IV (16) + trailer (2) + padding (~15) + ICV (12)
OpenVPN UDP ~29 bytes UDP header (8) + OpenVPN header (1) + HMAC (20)
OpenVPN TCP ~41 bytes TCP header (20) + OpenVPN header (1) + HMAC (20)
WireGuard ~32 bytes UDP header (8) + WG header (16) + Poly1305 auth (16)