Calculate network address, broadcast address, subnet mask, host range, usable IPs and IP class from any CIDR notation.
Enter your figures and click Calculate to see your results.
Enter an IP address with CIDR prefix notation (e.g. 192.168.1.0/24) — all subnet details appear instantly.
Press the Calculate button. All results appear instantly — no page reload, no waiting.
Results appear in the panel on the right with all key values clearly labelled. Use Copy to grab the result or Download to save a text file.
The /24 is the CIDR prefix length — the first 24 of the 32 IP address bits are the network portion. This leaves 8 bits for hosts: 2⁸ = 256 total addresses. Subtract 2 (network address and broadcast) = 254 usable host addresses. The subnet mask is 255.255.255.0.
The network address (all host bits = 0) identifies the subnet and cannot be assigned to a device. The broadcast address (all host bits = 1) sends messages to every device on the subnet and also cannot be used as a host. These two reserved addresses reduce usable hosts by 2: a /24 gives 254 usable hosts, not 256.
Usable hosts = 2^(32−prefix) − 2. Examples: /30 = 2 hosts (point-to-point links), /29 = 6 hosts, /28 = 14 hosts, /27 = 30 hosts, /26 = 62 hosts, /25 = 126 hosts, /24 = 254 hosts, /23 = 510 hosts, /22 = 1,022 hosts, /16 = 65,534 hosts, /8 = 16,777,214 hosts.
Subnetting divides a larger network into smaller segments to: improve security (isolate departments and limit broadcast traffic), reduce congestion (smaller broadcast domains), enable more efficient IP address use, and simplify network management and troubleshooting.
RFC 1918 defines three private (non-routable) IP address ranges: 10.0.0.0/8 (Class A, 16.7 million addresses), 172.16.0.0/12 (Class B, ~1 million addresses) and 192.168.0.0/16 (Class C, 65,536 addresses). These are used in home and corporate networks and are translated to public IPs via NAT when accessing the internet.
