IPv6 subnet calculator

Free IPv6 CIDR calculator. Enter a prefix like 2001:db8::/32 and get the network address, last address, expanded form, and address count.

Free tool

IPv6 Subnet Calculator

Enter an IPv6 prefix and get the exact network boundaries — compressed and expanded forms, the last address in the block, and the address count. Computed locally with 128-bit integer math, so the numbers are exact even for a /8.

IPv6 subnet calculator

Why is a /64 the standard IPv6 subnet?

IPv6 auto-configuration (SLAAC) requires 64 bits for the host part, so nearly every LAN gets a /64 — 18.4 quintillion addresses per subnet by design, not by need.

What is the expanded form of an IPv6 address?

The full eight groups of four hex digits with nothing omitted. The compressed form drops leading zeros and collapses one run of zero groups into ::. Both name the same address.

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