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CIDR Calculator

The CIDR Calculator turns any IPv4 CIDR block into its network and broadcast addresses, subnet mask, wildcard mask, usable host range and total host count. It uses pure bitwise arithmetic in your browser, with no network request and no signup.

Last updated · Free, no signup

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What does a CIDR calculator determine?

A CIDR calculator expands an IPv4 address and prefix length into its network address, broadcast address, subnet and wildcard masks, first and last usable hosts, and address counts. It helps plan subnets, review firewall ranges, and understand which addresses belong to a route.

All calculations use local bitwise arithmetic for prefixes from /0 through /32. The /31 and /32 cases follow RFC 3021-style point-to-point and host-route behavior by treating available addresses as usable. The tool covers IPv4 only and does not inspect whether a range is routed, allocated, or reachable.