IPv6 Subnet Calculator
Enter an IPv6 address with a prefix such as 2001:db8::1/48 and get the network range, both notations of the address, its type and the ip6.arpa name for reverse DNS.
- Compressed address
- 2001:db8:85a3::8a2e:370:7334
- Expanded address
- 2001:0db8:85a3:0000:0000:8a2e:0370:7334
- Network
- 2001:db8:85a3::/64
- Address range
- 2001:db8:85a3:: – 2001:db8:85a3:0:ffff:ffff:ffff:ffff
- Addresses in subnet
- 18,446,744,073,709,551,616 (2^64)
- /64 subnets inside
- 1
- Prefix mask
- ffff:ffff:ffff:ffff:0000:0000:0000:0000
- Address type
- Documentation (2001:db8::/32)
- Reverse DNS name
- 4.3.3.7.0.7.3.0.e.2.a.8.0.0.0.0.0.0.0.0.3.a.5.8.8.b.d.0.1.0.0.2.ip6.arpa
About this tool
IPv6 addresses are 128 bits written as eight groups of four hexadecimal digits. Leading zeros in a group may be dropped and one run of all-zero groups may be replaced by ::, which is why the same address can look very different. RFC 5952 defines the canonical short form: lowercase, the longest zero run collapsed, and no :: for a single zero group. This calculator shows both the fully expanded and the canonical compressed form.
Prefixes work as in IPv4 but the numbers are far larger: a /64, the standard size for one LAN, holds 2^64 addresses, and a /48 allocation contains 65,536 of those /64 networks. The tool also recognises special ranges such as link-local fe80::/10, unique local fc00::/7, multicast ff00::/8, IPv4-mapped ::ffff:0:0/96 and the documentation prefix 2001:db8::/32, and it builds the nibble-reversed name used for PTR records.
Frequently asked questions
- How many /64 subnets does a /48 contain?
- 65,536. Each step of the prefix doubles the count, so a /56 contains 256 and a /60 contains 16.
- Why is the compressed form different from what I typed?
- The calculator prints the RFC 5952 canonical form: lowercase, the longest run of zero groups replaced by ::, and leading zeros removed.
- Does it handle IPv4-mapped addresses?
- Yes. ::ffff:192.0.2.1 is parsed with its embedded IPv4 address and identified as IPv4-mapped.
- What is the reverse DNS name?
- The address written as 32 reversed hexadecimal nibbles under ip6.arpa. It is what a PTR record for the address must be named.