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IP/24SubnetLens

IPv6 subnet calculator

Prefix, interface space and address count for any IPv6 network, with expanded and compressed forms a click from your clipboard.

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2001:db8:abcd:12::/64
Entered2001:db8:abcd:12::42
2^64addresses in this prefix
First usable
2001:db8:abcd:12::
Last usable
2001:db8:abc…ff:ffff:ffff
Subnet 2001 colon db8 colon abcd colon 12 colon colon slash 64. 2 to the power 64 total addresses. First usable 2001 colon db8 colon abcd colon 12 colon colon , last usable 2001 colon db8 colon abcd colon 12 colon ffff colon ffff colon ffff colon ffff. The entered address 2001 colon db8 colon abcd colon 12 colon colon 42 sits at offset 66 inside the block.
Addresses in prefix2^64 total
2^64
Common
Broadcast
None
IPv6 has no broadcast.
Addresses
2^64
2^64 total
Bits
64 prefix/64 interface

No broadcast, no reserved pair

IPv6 has no broadcast address — that job belongs to multicast — so the block has one edge rather than two, and the whole prefix is addressable. Address counts are shown as powers of two, because a /64 holds 18.4 quintillion addresses and writing that out helps nobody.

Why /64 keeps appearing

A /64 is the standard size for a single IPv6 link: stateless address autoconfiguration expects 64 bits of interface identifier. Sites are usually delegated a /48 or /56 and then carved into /64s. Every calculation here uses 128-bit arithmetic throughout, so a /112 is exactly as accurate as a /64.