IP Calculator

Subnetting is one of those tasks that's simple in principle and error-prone in practice. Given an address and a prefix length, you need the network address, the broadcast address, the usable host range, and the total host count — and getting any of them wrong can mean an overlapping subnet, a firewall rule that's too broad, or a route that black-holes traffic. This calculator does the bit arithmetic for you and shows the result in binary, decimal, and hexadecimal so you can see exactly where the network and host boundaries fall.

Enter an IPv4 address with a CIDR prefix or subnet mask and the tool breaks down the network: it identifies the address class, the network and broadcast addresses, the first and last usable hosts, and how many hosts the subnet holds. For IPv6, it expands and compresses addresses, shows the prefix, and flags special-purpose ranges so you can tell a link-local address from a global unicast one at a glance.

Everything runs in your browser, so internal addressing plans and infrastructure details never leave your machine. That makes it safe to paste production CIDR blocks while planning a network, reviewing a security group, or debugging why two hosts can't reach each other.