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Subnet / CIDR calculator

Work out network, broadcast, host counts, and ranges for IPv4 and IPv6.

The subnet calculator does the CIDR math for you, entirely in your browser, no network calls. It handles both IPv4 and IPv6.

What it computes

  • Network and broadcast addresses (IPv4).
  • First and last usable host, and total host count.
  • The full address range for an IPv6 prefix.
203.0.113.0/24  ->  256 addresses, hosts .1 to .254
2a0e:xxxx::/44  ->  first 2a0e:xxxx::, 2^84 addresses

Open it under Tools → Subnet.