Subnet / CIDR calculator
Subnetting splits a large IP block into smaller, manageable networks. This calculator does all the math for you: enter an IPv4 address and a CIDR prefix length (or a subnet mask) and you'll get the network address, broadcast address, first and last usable host, total addresses in the range, usable hosts after subtracting network and broadcast, the subnet mask in dotted-decimal, and the wildcard mask. Useful for network planning, ACL writing, and decoding what a `/24` or `/16` actually contains. All calculations happen in your browser, no external service is queried.
Frequently asked questions
It's the number of bits at the front of the IPv4 address used for the network portion. A /24 means 24 bits identify the network and 8 bits identify the host within it, giving 256 addresses (254 usable). A /16 gives 65,536 addresses. Lower prefix means bigger network.
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