IPv6 Subnet Calculator
Work out the network, address range and count for an IPv6 prefix.
Calculated live in your browser.
Frequently asked questions
What does this calculate?
Enter an IPv6 address with a prefix length (like 2001:db8::/64) and it shows the network address, the first and last addresses in the block, the prefix, and the total number of addresses.
Why is the address count so huge?
IPv6 uses 128-bit addresses, so even a single /64 subnet contains 18.4 quintillion addresses. The calculator uses big-integer maths to show the exact count.
What is a /64 and why is it common?
A /64 is the standard size for a single IPv6 subnet or LAN, because stateless address autoconfiguration (SLAAC) expects 64 bits of host space. Providers often hand out /48 or /56 blocks made of many /64s.
What is the difference between expanded and compressed form?
Expanded form shows all eight 16-bit groups with leading zeros; compressed form drops leading zeros and collapses one run of zero groups to :: for readability. Both represent the same address.
Does it run on a server?
No. All the maths happens in your browser, so nothing you enter is sent anywhere.
Can I use it for prefix planning?
Yes. It is handy for confirming the boundaries and size of a subnet when you carve a larger allocation into smaller prefixes.