IPv6 Subnet Calculator
Free IPv6 subnet calculator and IPv6 CIDR calculator. Enter an IPv6 address with a prefix (for example 2001:db8:abcd:12::1/64) to get the network, address range, size and reverse DNS zone.
Split this network into smaller subnets
How to use the IPv6 subnet calculator
- Type an IPv6 address. Shortened forms like
2001:db8::1work, and so do embedded IPv4 forms like::ffff:192.0.2.1. - Add the prefix after a slash (
/48,/56,/64) or pick it from the list. - Press Calculate, then use Split this network to plan smaller subnets.
Common IPv6 prefix sizes
| Prefix | Typically used for | Number of /64 subnets |
|---|---|---|
| /32 | Allocation to an ISP or large organisation | 4,294,967,296 |
| /48 | A site or business | 65,536 |
| /56 | A home or small office connection | 256 |
| /60 | Some home ISP connections | 16 |
| /64 | A single LAN or VLAN (needed for SLAAC) | 1 |
| /127 | Point-to-point router links (RFC 6164) | – |
| /128 | A single address (loopback, host route) | – |
IPv6 address types
| Prefix | Type |
|---|---|
| 2000::/3 | Global unicast (public internet) |
| fc00::/7 | Unique local addresses (private, like RFC 1918 in IPv4) |
| fe80::/10 | Link-local (only valid on one network segment) |
| ff00::/8 | Multicast |
| 2001:db8::/32 | Documentation and examples |
| ::1/128 | Loopback |
| ::ffff:0:0/96 | IPv4-mapped addresses |
How IPv6 addresses are shortened
Each IPv6 address has eight groups of four hex digits. Leading zeros in a group can be dropped, and one run of all-zero groups can be replaced with ::. So 2001:0db8:0000:0000:0000:0000:0000:0001 becomes 2001:db8::1. This calculator follows RFC 5952, the standard for writing IPv6 addresses.
Working with IPv4 too? Use our IPv4 subnet calculator.
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Stay current on the threats these tools help defend against: read the latest vulnerability news, threats and malware and data breach coverage on Cyber Strike News.
Frequently asked questions
What is an IPv6 subnet calculator?
It takes an IPv6 address and prefix length and shows the network address, first and last address, the size of the network and the reverse DNS zone.
Why is /64 the standard IPv6 subnet size?
IPv6 stateless address autoconfiguration (SLAAC) needs a 64-bit interface ID, so LANs and VLANs almost always use a /64.
How many /64 subnets are in a /48?
A /48 contains 65,536 /64 subnets, because 2 to the power of (64 – 48) is 65,536.
Does IPv6 have a broadcast address?
No. IPv6 has no broadcast. It uses multicast instead, so every address in a subnet can be assigned.
What is the IPv6 equivalent of a private IP address?
Unique local addresses in fc00::/7 (in practice fd00::/8) play the role of private RFC 1918 addresses in IPv4.
Is my address sent anywhere when I use this tool?
No. All calculations run in your browser. Nothing you type is sent to a server or stored.