Subnet Calculator

Every IP network has a subnet mask that defines which portion of the IP address identifies the network and which identifies the host. CIDR notation (e.g. 192.168.1.0/24) compactly expresses this: the number after the slash is the count of network bits. A /24 means 24 bits for the network, 8 for hosts—256 addresses total, 254 usable (network and broadcast are reserved). This Subnet Calculator takes an IP and CIDR (or subnet mask) and returns network address, broadcast address, first and last usable IP, and host count.

Enter 192.168.1.0/24 and you get network 192.168.1.0, broadcast 192.168.1.255, first usable 192.168.1.1, last usable 192.168.1.254, and 254 hosts. The tool also accepts the older format: IP plus subnet mask (e.g. 10.0.0.0 255.255.255.0). Use it when designing networks, configuring firewalls, or troubleshooting. DevOps and system administrators use it to plan address space, verify firewall rules, or explain network layout to colleagues.

Understanding subnet boundaries prevents misconfiguration. A host with an IP outside the usable range will not communicate correctly. Firewall rules often reference network addresses; getting the range right is critical. For larger networks, /16 or /8 give more hosts; for small segments, /28 or /29 limit the size. The calculator shows the exact range so you can allocate IPs correctly. All math runs in your browser. No server, no storage. Enter any valid IP and CIDR combination.

CIDR from /0 to /32 is supported. /32 is a single host; /31 is sometimes used for point-to-point links. /30 gives 2 usable hosts. The tool handles edge cases and validates input. For quick checks during setup or debugging, this is faster than opening a terminal or lookup site. Bookmark it for the next time you need to verify a subnet.