IPv6 Subnet Calculator & Address Expander
Free IPv6 calculator: expand or compress any IPv6 address, calculate the subnet range for a prefix (/64, /56, /48…) and identify the address type.
Expand, compress and subnet IPv6 addresses
IPv6 addresses can be written many ways — 2001:0db8:0000:0000:0000:0000:0000:0001 and 2001:db8::1 are the same address. This tool converts between the expanded and RFC 5952 canonical compressed forms, identifies the address type (global unicast, link-local, unique local, multicast), and computes the full range covered by any prefix length.
Typical allocations: your ISP delegates a /56 or /48 to your site, and each LAN gets a /64 — which alone contains 18 quintillion addresses. New to the notation? Read how to read an IPv6 address and IPv4 vs IPv6.
Frequently asked questions
Why is everything a /64?
IPv6 standards expect the last 64 bits to identify the interface (SLAAC auto-configuration requires it), so /64 is the standard size for a single network segment regardless of how few devices it has.
What does :: mean?
A double colon compresses one run of consecutive zero groups. It can appear only once per address, so the notation stays unambiguous.