CIDR Subnet Calculator
Pure frontend: enter a network, instantly get network address, broadcast address, netmask and usable IP range. Nothing leaves your browser — no network call, nothing recorded.
How to use
Enter a CIDR network (e.g. 192.168.1.0/24) and hit Calculate to get the full subnet info. Prefix 0–32 is supported.
Common subnet reference
| Prefix | Netmask | Total addresses | Usable hosts | Typical use |
|---|---|---|---|---|
| /24 | 255.255.255.0 | 256 | 254 | Regular LAN |
| /25 | 255.255.255.128 | 128 | 126 | Small segment |
| /26 | 255.255.255.192 | 64 | 62 | Small team |
| /27 | 255.255.255.224 | 32 | 30 | Small device segment |
| /30 | 255.255.255.252 | 4 | 2 | Point-to-point link |
| /31 | 255.255.255.254 | 2 | 2 | Point-to-point (RFC 3021) |
| /32 | 255.255.255.255 | 1 | 1 | Single host / host route |
Why /31 and /32 are special
A normal subnet reserves the first and last address for network and broadcast, which is why a /30 has only 2 usable IPs — the classic point-to-point setup. But per RFC 3021, a /31 on a point-to-point link treats both addresses as hosts, dropping the broadcast reservation. A /32 is a single host address, common for host routes or exact prefixes.
Related tutorials
- TCP/IP state machine & troubleshooting — read every column of
ss/netstat, pair with subnetting to understand segment boundaries - DNS resolution & caching — the resolution chain after you plan your address space