CIDR Calculator
Network, broadcast and usable host range, for IPv4 and IPv6.
Subnet details
Examples
Questions
Does the address have to be the start of the subnet?
No. 192.168.1.130/26 gives the same result as 192.168.1.128/26. The host bits are masked off first, as routers do.
Why do /31 and /32 have no broadcast address?
A /32 is a single host. A /31 is for point-to-point links (RFC 3021), where both addresses are usable hosts.
Why does IPv6 show no broadcast address?
IPv6 has no broadcast. It uses multicast instead, so every address in the range is usable, including both ends.
How large can an IPv6 subnet be?
A /0 holds 2^128 addresses, a 39-digit number. The tool counts it exactly with BigInt.