IP Subnet Calculator
Enter an IPv4 address with a CIDR prefix, like 192.168.1.10/24 — the subnet details update as you type.
What this tool does
This tool takes an IPv4 address and a CIDR prefix (the "/24" after the address) and calculates everything you need to know about that subnet: the network address, broadcast address, subnet mask, wildcard mask, the range of usable host addresses, and the total and usable address counts. Results update live as you type, and all math happens locally in your browser.
Example use case
Network engineers and developers use subnet calculators when planning IP address ranges, configuring
firewall rules, or figuring out whether two hosts are on the same subnet. For example, entering
192.168.1.10/24 shows that the usable host range is 192.168.1.1 through
192.168.1.254, with 192.168.1.0 reserved as the network address and
192.168.1.255 reserved as the broadcast address.
Note on small prefixes
For a /31 prefix (point-to-point links per RFC 3021), both addresses are usable since there's no network or broadcast address reserved. For a /32, the single address is the host itself.