MSS Calculator

Derive TCP maximum segment size from MTU, IP version, and TCP timestamps.

MTU

IPv6 Timestamps

MSS1460 B

Subtracted20 (IPv4) + 20 (TCP)

How to read the result

MSS = MTU − IP header (20 IPv4 / 40 IPv6) − TCP header (20) − timestamps (12 if enabled).

Example

MTU 1500 IPv4 → MSS 1460

FAQ

Why 1460 for Ethernet?

1500 − 20 (IPv4) − 20 (TCP) = 1460. IPv6 gives 1440; timestamps subtract 12 more.

MSS vs MTU?

MTU is the whole IP packet limit; MSS is the TCP payload limit inside it.