An IP subnet calculator is a tool that helps network engineers and administrators quickly compute network details from an IP address and its CIDR prefix length. Given an input like 192.168.1.0/24, it calculates the network address, broadcast address, subnet mask, usable host range, and more.
CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length, written as IP/prefix. The prefix indicates how many bits of the address identify the network. For example, /24 means the first 24 bits are the network portion, leaving 8 bits (256 addresses) for hosts.
IPv4 addresses are 32-bit numbers, typically written as four decimal octets (e.g. 192.168.1.0). IPv6 addresses are 128-bit numbers written in hexadecimal groups (e.g. 2001:db8::1). This calculator supports both formats and adjusts its output accordingly - for example, IPv6 networks do not use broadcast addresses or wildcard masks.
| CIDR | Subnet Mask | Usable Hosts | Common Use |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | Single host |
| /31 | 255.255.255.254 | 2 | Point-to-point link |
| /30 | 255.255.255.252 | 2 | Small WAN link |
| /24 | 255.255.255.0 | 254 | Small network / LAN |
| /16 | 255.255.0.0 | 65,534 | Medium network |
| /8 | 255.0.0.0 | 16,777,214 | Large network (Class A) |