Enter a CIDR block to find the first and last IP address in the range, the total number of addresses, and the equivalent subnet mask.
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A CIDR block like 192.168.1.0/24 combines an IP address with a prefix length (the /24) that defines how many leading bits are fixed for the network. This calculator masks the address down to its network boundary, then sets all the remaining bits to 1 to find the last address in the block, giving you the full inclusive range the CIDR block covers.
This is useful when reviewing firewall rules, cloud security groups, or access control lists that reference CIDR blocks, letting you quickly see exactly which IP addresses a given rule covers, or how many total addresses (including network and broadcast) a block contains.
Yes, the first and last address shown are the full inclusive range of the CIDR block, including the network address and broadcast address. Use the Subnet Calculator if you need the usable host range excluding those two addresses.
Enter the block as an IP address followed by a forward slash and the prefix length, for example 10.0.0.0/16 or 192.168.1.0/24.
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