Free subnet calculator: enter an IPv4 address and CIDR prefix for the mask, network, broadcast, host range and usable hosts.
Pure math on the address you enter — nothing is sent anywhere. /31 subnets (point-to-point links) and /32 (single host) follow RFC 3021 conventions.
This subnet calculator takes any IPv4 address plus a CIDR prefix (1–32) and instantly derives the full subnet picture: subnet mask, wildcard mask, network and broadcast addresses, first and last usable hosts, the usable host count, the IP class, and the binary of each octet. Type an address or drag the CIDR slider — every result updates live.
Subnetting divides an IP network into smaller pieces by borrowing host bits for the network portion. The CIDR prefix (the “/24” in 192.168.1.0/24) says how many of the 32 bits belong to the network. The subnet mask writes that as dotted decimal (255.255.255.0), and the wildcard mask is its bitwise inverse (0.0.0.255) — used in router ACLs. The network address (all host bits 0) identifies the subnet, the broadcast address (all host bits 1) reaches every host on it, and the addresses between are usable hosts. IP classes (A/B/C/D/E) are the legacy grouping by first-octet range, and the calculator also flags private (RFC 1918) vs public space.
Subnet mask: 32-bit number with the first prefix bits set to 1, written in dotted decimal.
Wildcard mask: bitwise NOT of the subnet mask.
Network address: IP AND subnet mask.
Broadcast address: network address OR wildcard mask.
Usable hosts: 2^(32 − prefix) − 2 (network and broadcast excluded; /31 gives 2 point-to-point hosts, /32 is a single host).
Worked example. 192.168.1.130/24:
A small business has 192.168.10.0/24 and wants four subnets for staff, guests, servers, and IoT. Borrowing 2 host bits gives a /26: mask 255.255.255.192, 2^6 − 2 = 62 usable hosts per subnet. The four networks are 192.168.10.0, .64, .128, and .192, with broadcasts .63, .127, .191, and .255. Drag the calculator’s slider from /24 to /26 on any of these addresses to verify each boundary — a five-second check that beats manual binary math when you’re configuring VLANs or DHCP scopes.
Decimal to Binary Converter — convert any number to binary for manual subnet math.
Binary to Decimal Converter — go the other way when checking masks by hand.
Octal to Decimal Converter — another base-conversion tool for low-level work.
Scientific Calculator — powers of two and bitwise-style arithmetic.
Password Generator — another practical tool from the Technology hub.
This page hosts a free Subnet Calculator that takes an IPv4 address and a CIDR prefix (1–32) and computes the subnet mask, wildcard mask, network address, broadcast address, first and last usable host, usable host count (2^(32−prefix) − 2), IP class, private/public scope, and binary octets. Key facts: the network address is the IP ANDed with the mask; the broadcast is the network ORed with the wildcard; /31 subnets allow 2 point-to-point hosts and /32 is a single host. Example: 192.168.1.130/24 yields mask 255.255.255.0, network 192.168.1.0, broadcast 192.168.1.255, 254 usable hosts, Class C, private.
Set the first N bits of a 32-bit number to 1 (where N is the CIDR prefix) and write it in dotted decimal. For /24, that’s 24 ones = 255.255.255.0. For /26, it’s 26 ones = 255.255.255.192. The wildcard mask is the inverse: 0.0.0.63 for /26.
254. The formula is 2^(32 − prefix) − 2: a /24 has 8 host bits, so 2^8 = 256 addresses minus the network and broadcast addresses = 254 usable hosts.
The network address (all host bits 0, e.g. 192.168.1.0) identifies the subnet itself and can’t be assigned to a device. The broadcast address (all host bits 1, e.g. 192.168.1.255) sends a packet to every host on the subnet. Usable device addresses are everything in between.
A wildcard mask is the bitwise inverse of the subnet mask (e.g. 0.0.0.255 for a /24). It is used in router access control lists (ACLs) and OSPF/EIGRP network statements to specify which address bits must match, giving more flexible matching than a subnet mask alone.
RFC 1918 defines three private ranges: 10.0.0.0/8 (10.0.0.0–10.255.255.255), 172.16.0.0/12 (172.16.0.0–172.31.255.255), and 192.168.0.0/16 (192.168.0.0–192.168.255.255). These are not routable on the public internet and are used for home and office networks behind NAT.
Cite this page as: “Subnet Calculator.” Sigma Calculator. Accessed October 20, 2026. https://sigmacalculator.net/technology-calculators/subnet-calculator/
Last updated: October 20, 2026