Subnet Calculator
IPv4 and IPv6 CIDR calculator. Everything is calculated in your browser — nothing you type is sent to the server.
Examples: 192.168.10.77/26 · 10.0.0.1 255.255.240.0 · 100.64.0.0/10 · 2001:db8:abcd::/48
Frequently asked questions
What does /24 mean?
CIDR notation: the number after the slash is how many leading bits are the network part. A /24 leaves 8 bits for hosts — 256 addresses, of which 254 are usable hosts in IPv4 (the first is the network address, the last the broadcast).
What is a wildcard mask?
The bitwise inverse of the netmask (255.255.255.0 → 0.0.0.255). Cisco ACLs and OSPF use it to say which bits may vary.
Why do /31 and /32 show no broadcast address?
A /32 is a single host. A /31 is a point-to-point link where both addresses are usable hosts (RFC 3021), so neither is reserved for network or broadcast.
Does IPv6 have a broadcast address?
No. IPv6 uses multicast instead, so every address in the range is usable. LANs are almost always /64.