Enter an IPv4 address in CIDR notation to instantly compute network address, broadcast address, usable host range, subnet mask, wildcard mask, and binary representations. Everything runs locally in your browser.
192.168.1.0/24) and click Calculate192.168.1.0/24 means the first 24 bits are the network portion and the remaining 8 bits identify individual hosts. You can also enter a host address like 10.10.5.100/28 — the calculator will show you which network that host belongs to.An IPv4 address is a 32-bit number typically written in dotted-decimal notation (e.g. 192.168.1.1). A subnet divides a network into smaller segments. The prefix length (written after the slash in CIDR notation) tells you how many leading bits of the address identify the network versus individual hosts.
For example, a /24 prefix means the first 24 bits are fixed (the network) and the remaining 8 bits can vary (the hosts). This gives 28 = 256 total addresses, of which 254 are usable (the first is the network address and the last is the broadcast address). Subnetting is fundamental to IP routing, firewall rules, VPC configuration in cloud environments, and network segmentation for security.
The three private IP ranges defined in RFC 1918 are: 10.0.0.0/8 (Class A, ~16 million hosts), 172.16.0.0/12 (Class B, ~1 million hosts), and 192.168.0.0/16 (Class C, ~65,000 hosts). These are used in home networks, corporate intranets, and cloud VPCs and are not routable on the public internet.
The network address is the first address in a subnet (all host bits set to 0). It identifies the subnet itself and cannot be assigned to any host. The broadcast address is the last address (all host bits set to 1). Packets sent to this address are delivered to every host on the subnet. Both are reserved, so the number of usable host addresses in a /N subnet is 232-N − 2. A /30 subnet, commonly used for point-to-point links, has only 2 usable addresses.
A wildcard mask is the bitwise complement of the subnet mask. Where the subnet mask has a 1 bit (fixed/network bit), the wildcard mask has 0, and vice versa. Wildcard masks are used in Cisco ACLs (Access Control Lists) and OSPF configurations to specify which bits of an IP address must match exactly. For example, a subnet mask of 255.255.255.0 corresponds to a wildcard of 0.0.0.255, meaning the first three octets must match and the last octet can be anything.
CIDR stands for Classless Inter-Domain Routing. It was introduced in 1993 (RFC 1519) to replace the original class-based addressing system (Class A /8, Class B /16, Class C /24) which was causing rapid exhaustion of IPv4 addresses. CIDR allows networks to be allocated in arbitrary prefix lengths (e.g. /22, /27), enabling far more efficient use of the address space. It also introduced route aggregation (supernetting), which dramatically reduced the size of internet routing tables.
A /32 is a host route — it identifies exactly one IP address (zero hosts, zero broadcast, just the single address). A /31, defined in RFC 3021, is used for point-to-point links and has 2 addresses with no dedicated network or broadcast address, giving 2 usable hosts. This tool follows RFC 3021 for /31 (both addresses are shown as usable) and treats /32 as a single-host route.