Subnet and PortsIPv6 subnet calculator
IPv6 addresses are long. This tool shortens them correctly, and shows the range and size of any prefix.
What you can type
An IPv6 address in any legal form: full (2001:0db8:0000:0000:0000:ff00:0042:8329), shortened (2001:db8::ff00:42:8329), or with an IPv4 address at the end (::ffff:192.0.2.1), optionally followed by a slash and a prefix length from 0 to 128. Without a prefix, the tool uses /128, a single address.
Reading the result
Shortest form. The tool applies the rules of RFC 5952, the recommended text form: letters in lower case, no leading zeros in a group, and the longest run of two or more all-zero groups replaced by :: (the first one if there is a tie). Using one standard form makes addresses easy to search for and compare.
Full form. Eight groups of four hexadecimal digits, as the address is stored.
Network, first and last address. For a prefix, the first address has all remaining bits zero and the last has them all one. IPv6 has no broadcast address, so the last address is an ordinary one.
Addresses in the block and /64 subnets. The numbers are huge, which is why they are shown with separators. A normal IPv6 subnet for a LAN is a /64, so the count of /64 subnets tells you how many LANs a bigger block can serve.
Type. The tool looks in the IANA IPv6 special-purpose address registry (loopback ::1, unspecified ::, documentation 2001:db8::/32, unique local fc00::/7, link-local fe80::/10, and others) and labels multicast ff00::/8.
Typical prefix lengths
| Prefix | What it is usually used for |
|---|---|
| /128 | One address (a host route, a loopback) |
| /64 | One LAN subnet, the normal size |
| /56 or /48 | What an internet provider often gives to a home or a site |
| /32 | A block for a service provider |
These are conventions in common use rather than rules; check what your provider gives you.
Common mistakes
- Using more than one
::. It can appear only once, otherwise the address would be ambiguous. - Dropping zeros from the end of a group (
2001:db8:1is not2001:db80:1). Only leading zeros in a group can be omitted. - Using /64 networks smaller than /64 for ordinary LANs. Many IPv6 features assume 64 bits for the host part.
We checked this tool against Python's ipaddress on 400 random IPv6 addresses and prefixes, comparing the short form, the full form, the network and the last address; all matched.
Is there a broadcast address in IPv6?
No. IPv6 uses multicast instead.
Why does the tool change my uppercase letters?
RFC 5952 recommends lower case, so the output is consistent.
This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.