Subnet Calculator

How to use

1. 1Pick CIDR notation (one field like 192.168.1.0/24) or IP and mask (two fields like 192.168.1.10 and 255.255.255.0).
2. 2Type or paste your address. The summary, address details, and binary breakdown update as you type.
3. 3Click a quick sample (Home / SOHO, Class C, Small office, Class B, /30 link, /31 P2P) to load a typical block in one click.
4. 4Read the network and broadcast addresses, first and last usable host, mask, wildcard, total addresses, usable host count, and the Range type label (Class, Private, Loopback, Link-local, Multicast).
5. 5Use the binary breakdown to see how many bits identify the network vs the host. Copy any single field with the Copy button.

About this tool

Subnet Calculator is an IPv4 network calculator that runs entirely in your browser. Enter a CIDR like 192.168.1.0/24, or pick the IP and mask mode and enter an address with its dotted subnet mask, and the tool reports the network address, broadcast address, first and last usable host, total addresses, usable host count, subnet mask in dotted decimal, wildcard mask (the inverse used in router ACLs), the prefix length, and a hex view of the network address. Inputs are validated octet by octet so leading-zero or out-of-range values are flagged with a clear error, and the mask mode rejects non-contiguous masks (anything other than N ones followed by 32 minus N zeros). The tool handles the common edge cases correctly: a /32 prefix is treated as a single host route with no broadcast, a /31 link is treated as an RFC 3021 point-to-point pair where both addresses are usable and there is no broadcast, and a /0 prefix labels the result as the default route or every IPv4 address. The Range type line tags the network as Class A, B, C, D (multicast), or E (reserved), and adds Private (RFC 1918) for the 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 ranges, Loopback for 127.0.0.0/8, Link-local for 169.254.0.0/16, and Multicast for the 224.0.0.0/4 block, so you can tell at a glance whether a block is routable on the public internet or reserved for a specific use. Below the address details, a binary breakdown shows the network, mask, broadcast, and wildcard in 32 bits split into four octets, with the first prefix bits highlighted as network bits and the rest as host bits, making it easy to see how many bits identify the subnet versus the host. Useful when you are sizing a VLAN, planning DHCP scopes, writing an ACL or firewall rule, learning subnetting for a CCNA or Network+ exam, or normalizing a CIDR pasted from another tool. Validation, bit math, and rendering all happen on your device, so the addresses you paste here, including production network plans, never leave your browser.

Free to use. Works in your browser. No signup, no login.