IPv4 subnet calculator
Work out network address, broadcast, mask, host range and size from CIDR.
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About the ipv4 subnet calculator
Works out the network and broadcast addresses, usable host range, host count, wildcard mask and address class from any CIDR block or address-and-mask pair. A binary view shows exactly where the prefix boundary falls, and /31 and /32 are handled correctly.
Frequently asked questions
Why are two addresses unusable in a subnet?
The first identifies the network itself and the last is the broadcast address. A /24 therefore offers 254 usable hosts out of 256. Point-to-point /31 links are the documented exception.
How many hosts does a /22 hold?
1024 addresses, 1022 usable. Each bit you take from the prefix doubles the block, so /23 is 512 and /21 is 2048.