IPv6 Subnet & Prefix Calculator
Enter an IPv6 prefix like 2001:db8::/48 to see its range, size and how it splits into /56 or /64 networks.
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Frequently Asked Questions
65,536. Each extra prefix bit halves the size, and a /48 has 16 bits before /64.
SLAAC auto-configuration expects 64-bit interface IDs, so almost every IPv6 LAN is a /64.
Link-local addresses, configured automatically on every interface and never routed.
Reverse the hex nibbles of the prefix and append ip6.arpa — the calculator shows it for you.
No. All subnet math runs in your browser. The IPs and networks you enter never leave your device.
No. All subnet math runs in your browser. The IPs and networks you enter never leave your device.