IPv6 Calculator
Expand, compress and analyze IPv6 addresses including prefix and interface identifier breakdown.
Inputs
Expanded Address
2001:0db8:85a3:0000:0000:8a2e:0370:7334
Compressed Address
2001:db8:85a3::8a2e:370:7334
Prefix Length
/64
Addresses in Subnet
2^64 = ~1.84e+19
Host Bits
64
Step by step
Expand address
2001:0db8:85a3::8a2e:0370:7334
= 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Identify prefix
First 64 bits
= /64
Host bits
128 - 64
= 64
Address space
2^64
= 2^64 = ~1.84e+19
How it works
IPv6 addresses are 128 bits written as eight groups of four hex digits. The '::' shorthand collapses consecutive all-zero groups. Expanding reverses this compression for analysis. The prefix length determines how many leading bits identify the network versus the interface.
Formula
Addresses in subnet
addresses = 2^(128 - prefix)
- p
- Prefix length in bits
Frequently Asked Questions
Why is /64 the most common IPv6 prefix?
IPv6 was designed with a 64-bit network prefix and 64-bit interface identifier split in mind. SLAAC (Stateless Address Autoconfiguration) requires a /64 subnet to derive interface IDs from MAC addresses, making /64 the standard subnet size for end-user networks.
How does '::' compression work?
A single '::' replaces one or more consecutive groups of all zeros. It can only appear once in an address to avoid ambiguity about how many groups were compressed.