How to Use the Network MTU & MSS Overhead Calculator
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1
Set your base interface MTU (default 1500 for standard Ethernet).
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2
Select IP version (IPv4 = 20-byte header, IPv6 = 40-byte header).
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3
Add encapsulation layers: PPPoE (+8 bytes), VLAN 802.1Q (+4 bytes), WireGuard (+32 bytes), IPsec ESP (+56+ bytes), or GRE (+24 bytes).
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4
View the computed TCP MSS (Maximum Segment Size) and maximum UDP payload without packet fragmentation.
Practical Example & Use Case
Common Real-World Scenario
Finding that a PPPoE broadband connection with MTU 1492 over IPv4 requires a TCP MSS of exactly 1452 bytes (1492 - 20 IP - 20 TCP).
Technical Notes & Limitations
Browser Engine Architecture
Based on standard RFC 791, RFC 8200, and RFC 879 protocol specifications.
Frequently Asked Questions
What happens if a packet exceeds the MTU?
If the Don't Fragment (DF) flag is set, the router drops the packet and sends an ICMP "Fragmentation Needed" message; otherwise, the packet is fragmented into multiple packets.