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CIDR calculator

Enter an IPv4 or IPv6 CIDR network. Host-prefix input such as 8.8.8.8/24 is accepted and normalized to the canonical network.

What this tool does

The CIDR calculator normalizes a network, calculates its first and last address, counts total addresses, and shows IPv4-specific netmask, broadcast, and usable host values.

Use it when a firewall, DNS provider, hosting panel, or network document gives you CIDR notation and you need the actual address range. Start with the CIDR notation guide if the slash number is unfamiliar.

CIDR notation explained A quick explanation of prefix lengths, host bits, and canonical networks. IP in CIDR Check whether one address belongs inside a network range. Range to CIDR Convert raw IP address ranges into CIDR blocks. Subnet splitter Divide a network into smaller subnets with a longer prefix.