IPv6 Subnet Calculator

Get the network, address range, total count and compressed/expanded form of any IPv6 prefix.

Updated: June 27, 2026

Work out any IPv6 prefix instantly

IPv6 addresses are 128 bits — four times the size of IPv4 — which makes them awkward to reason about by hand. Enter an address and prefix length (for example 2001:db8::/32) and this calculator gives you the network address, the first and last address in the block, the total number of addresses, both the compressed and fully expanded forms, and the address type. Everything is computed in your browser.

How IPv6 notation works

An IPv6 address is written as eight groups of four hexadecimal digits separated by colons. To keep it readable, two shortcuts apply: leading zeros in a group can be dropped, and one run of consecutive all-zero groups can be replaced by ::. So 2001:0db8:0000:0000:0000:0000:0000:0001 compresses to 2001:db8::1. The :: shortcut may appear only once, otherwise the address would be ambiguous. This tool shows both the compressed (RFC 5952) and expanded forms so you can see exactly what an address means.

Prefixes and the /64 convention

Like IPv4, IPv6 uses CIDR prefix notation, but the scale is enormous. A single /64 — the standard size for one subnet — contains 2⁶⁴ ≈ 18 quintillion addresses, far more than the entire IPv4 internet. Providers typically delegate a /48 or /56 to a site, which is then split into many /64 subnets. Because subnets are so large, IPv6 generally doesn't bother with the IPv4 idea of "usable hosts minus network and broadcast" — there's no broadcast address in IPv6 at all.

Address types you'll see

Global unicast (2000::/3) — routable, public IPv6 addresses.
Unique local (fc00::/7) — private addresses, the IPv6 equivalent of RFC 1918.
Link-local (fe80::/10) — valid only on the local link; every interface has one.
Multicast (ff00::/8) — one-to-many delivery (IPv6 has no broadcast).
Loopback (::1) and unspecified (::) — special single addresses.

IPv4 and IPv6 together

Most networks run dual-stack, so you'll plan both. Use this alongside our IPv4 subnet calculator when designing addressing, and double-check that any documentation prefixes (like 2001:db8::/32, reserved for examples) aren't accidentally used in production.

Frequently asked questions

How many addresses are in an IPv6 /64?

A /64 contains 2^64 — about 18.4 quintillion — addresses. That's why /64 is the standard size for a single IPv6 subnet, and why host-counting conventions from IPv4 don't really apply.

How does IPv6 address compression work?

You may drop leading zeros in each group, and replace one run of consecutive all-zero groups with '::'. The :: shortcut can appear only once. This tool shows both the compressed (RFC 5952) and fully expanded forms.

Does IPv6 have a broadcast address?

No. IPv6 replaces broadcast with multicast. That's one reason it doesn't use the IPv4 'network and broadcast reduce usable hosts' model — a subnet's whole range is addressable.

What is fe80:: used for?

fe80::/10 is the link-local range. Every IPv6 interface automatically gets a link-local address, used for on-link communication and protocols like neighbor discovery. It is not routable beyond the local link.

IPv6 planning & management

Managing IPv6 at scale benefits from proper tooling — the address space is too large for spreadsheets:

IP address management (IPAM) Plan and document IPv6 prefix delegation across sites, with hierarchy that matches the huge address space.
Network monitoring platform Discover and monitor dual-stack networks so IPv6 connectivity issues don't hide behind working IPv4.