IPv6 Subnet Calculator

IPv6 networks are handed out as prefixes — a /48 for a site, a /56 or /60 for a home, a /64 for each LAN — and the numbers involved are too large to work out by hand. Enter an address and prefix to get the network in compressed and full form, the first and last address, the exact number of addresses, how many /64 networks fit, and what kind of address it is. Choose a longer prefix to list the subnets inside it.

How to use this tool

1. Type an address with its prefix length, such as 2001:db8:abcd::/48 (any address inside the network works).
2. Choose the subnet size to split into — /64 for LANs is typical.
3. Set how many subnets to list (up to 256).
4. Copy the network, range or subnet list.

Formula

network = address AND mask · last = network OR NOT mask · addresses = 2^(128 − p) · subnets of /q = 2^(q − p)

Addresses are handled as exact 128-bit integers. Output follows RFC 5952: lower-case hex, leading zeros dropped and the longest run of two or more zero groups replaced by "::" (the first run if two are equally long). IPv6 has no broadcast address, so the whole range is usable apart from reserved interface IDs.

Example

2001:db8::/48 contains 2^80 = 1,208,925,819,614,629,174,706,176 addresses. Split into /64 networks it gives 2^16 = 65,536 subnets, from 2001:db8::/64 to 2001:db8:0:ffff::/64, and its last address is 2001:db8:0:ffff:ffff:ffff:ffff:ffff. The 2001:db8::/32 range is reserved for documentation, so it is labelled as such.