CIDR.SUBNET
[ READY ]Type a CIDR block — get network, broadcast, host range, mask, wildcard, total + usable hosts, and the binary breakdown. Works for IPv4 and IPv6.
Binary (network bits highlighted)
[01] Quick reference
| CIDR | Mask | Hosts | Common use |
|---|---|---|---|
/8 | 255.0.0.0 | 16,777,214 | RFC1918 10.0.0.0/8 private |
/12 | 255.240.0.0 | 1,048,574 | RFC1918 172.16.0.0/12 |
/16 | 255.255.0.0 | 65,534 | Class B / RFC1918 192.168.0.0/16 |
/24 | 255.255.255.0 | 254 | Typical LAN subnet |
/29 | 255.255.255.248 | 6 | Small point-to-point |
/30 | 255.255.255.252 | 2 | Router-to-router link |
/31 | 255.255.255.254 | 2 (RFC 3021) | P2P, no broadcast |
/32 | 255.255.255.255 | 1 | Single host route |
[02] How CIDR works
CIDR ("Classless Inter-Domain Routing") replaced the old A/B/C class system in 1993. Instead of fixed boundaries, the prefix length (the /N) tells you how many bits identify the network. Everything beyond those bits identifies the host.
For 192.168.1.0/24: the first 24 bits (192.168.1) are the network. The last 8 bits are host. That gives 28 = 256 addresses, of which 254 are usable hosts (network address and broadcast are reserved).
[03] IPv6 differences
IPv6 uses 128-bit addresses, written in 8 groups of 4 hex digits. Common prefixes: /48 (site), /56 (smaller site), /64 (single LAN — the default for SLAAC). There's no broadcast address and the network/host distinction works the same way at the bit level.