IPv6 Subnet Calculator

How the IPv6 subnet calculator works

IPv6 addresses are 128 bits long and written as eight groups of four hexadecimal digits. The calculator breaks an address with its prefix into its parts – both fully written out and in the short "::" notation.

• Expanded vs. compressed: 2001:db8::1 is the short form of 2001:0db8:0000:0000:0000:0000:0000:0001. "::" replaces exactly one run of zero groups.
• Network & address range: The prefix (e.g. /64) separates the network from the interface part. First and last address span the range.
• /64 networks: A /48 prefix contains 65,536 individual /64 networks – the usual size of a customer subnet.

The calculation runs entirely in the browser using 128-bit arithmetic (BigInt); no data is transmitted.

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