CIDR and subnet calculator
Network address, broadcast, usable range, mask and host count for any IPv4 prefix, plus what you get if you split it. Useful when a firewall change request says 10.0.0.0/22 and nobody wants to be the one who asks what that covers.
Everything you type stays in this tab. Share copies a link, never your inputs, unless the tool says it encodes them in the URL.
| Subnet | Range | Usable |
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A /31 carries two addresses and no broadcast, which RFC 3021 allows for point-to-point links, and a /32 is a single host. Both are shown as they really behave rather than as the arithmetic would suggest.