Subnet / CIDR Calculator

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Calculate network address, broadcast address, subnet mask, and usable host range from an IP and CIDR prefix.

Frequently asked questions

What does the prefix length (the /24 part) actually mean?

It's the number of leading bits in the 32-bit IP address reserved for the network portion — the remaining bits identify hosts within that network. A /24 reserves 24 bits for the network, leaving 8 bits (256 addresses) for hosts.

Why do /31 and /32 show 0 usable hosts?

A /32 is a single address with no room for a separate network/broadcast address, and a /31 (RFC 3021) is specifically designed for point-to-point links where both addresses in the pair are used directly, without a broadcast address in between.

Does this support IPv6?

No — this calculator is IPv4 only.

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