IPv6 Subnet Calculator
Enter an IPv6 address and prefix to see its network, range, size, type and reverse DNS zone, plus compressed and fully expanded forms.
- Expand & compress
- Network & range
- /64 count
- Address type
Common prefixes: /48 for a site, /56 for a home, /64 for a single LAN.
- Compressed
- 2001:db8:abcd:12::5
- Expanded
- 2001:0db8:abcd:0012:0000:0000:0000:0005
- Network
- 2001:db8:abcd::/48
- First address
- 2001:db8:abcd::
- Last address
- 2001:db8:abcd:ffff:ffff:ffff:ffff:ffff
- Addresses
- 1.208 × 10^24
- /64 subnets
- 65,536
- Address type
- Documentation (2001:db8::/32)
- Reverse DNS zone
- d.c.b.a.8.b.d.0.1.0.0.2.ip6.arpa
How IPv6 subnetting works
IPv6 addresses are 128 bits written as eight groups of four hex digits, usually shortened by dropping leading zeros and replacing one run of zero groups with ::. Networks are written with a prefix length: ISPs often delegate a /48 or /56 to a site, and each LAN uses a /64. This calculator expands and compresses addresses to RFC 5952 canonical form, finds the network and last address of a prefix, counts addresses and /64 subnets with exact big-number maths, identifies the address type and builds the ip6.arpa reverse zone.
How to calculate an IPv6 subnet
- Enter an IPv6 address with a prefix, e.g. 2001:db8::1/64.
- Adjust the prefix slider.
- Read the network, range, size and type.
- Copy the compressed or expanded form you need.
IPv6 prefix sizes
- /48: a typical site allocation, 65,536 /64 subnets.
- /56: common for home connections, 256 /64 subnets.
- /64: one LAN; SLAAC requires a /64.
- fc00::/7 is unique local (private), fe80::/10 link-local, 2000::/3 global unicast.
Why use this ipv6 subnet calculator
- Instant and exactResults update as you type, with copy buttons on every value.
- Learn as you goBinary view highlights the network and host bits so subnetting makes sense.
- Splitting built inDivide any network into equal smaller subnets and list each range.
- Nothing leaves your browserNetwork plans and internal addressing are calculated on your device, never logged by a server.
Common uses
- ISP delegations. See how many /64 LANs fit in your /48 or /56.
- DNS. Build ip6.arpa reverse zones.
- Firewall rules. Get the canonical prefix.
- Learning IPv6. See expanded and compressed forms side by side.
More network tools: convert addresses with the binary to decimal and hex to decimal converters, or test endpoints with the API tester. Browse all developer tools.
Example: 2001:db8:abcd:12::5/48
Network 2001:db8:abcd::/48 · Last address 2001:db8:abcd:ffff:ffff:ffff:ffff:ffff · 65,536 /64 subnets.
What to expect from the result
Zone IDs such as %eth0 are accepted but ignored. IPv6 has no broadcast address; every address in a /64 can be used by hosts.
IPv6 Subnet Calculator questions
How many /64 subnets are in a /48?
65,536 (2^16). A /56 contains 256 /64 subnets.
How do I expand a compressed IPv6 address?
Replace :: with enough zero groups to make eight, and pad each group to four hex digits. The calculator shows both forms.
Why is a /64 the standard IPv6 subnet?
Stateless address autoconfiguration (SLAAC) uses the last 64 bits for the interface identifier, so LANs use /64.
Is there a broadcast address in IPv6?
No. IPv6 uses multicast instead, so the whole range is usable.
What is a unique local address?
An address in fc00::/7 (usually fd00::/8), the IPv6 equivalent of private IPv4 ranges.