CIDR to IP Range Calculator

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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How It Works

How a CIDR block maps to an IP range

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.

Common uses for CIDR range lookups

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.

Worked example

Entering 192.168.1.0/24 gives a first address of 192.168.1.0, a last address of 192.168.1.255, a total of 256 addresses, and an equivalent subnet mask of 255.255.255.0. That total of 256 includes both the network address and the broadcast address, if you specifically need the usable host range excluding those two (254 hosts in this case), use the Subnet Calculator instead.

Common Mistakes to Avoid

Treating the total address count as the usable host count, this figure includes the reserved network and broadcast addresses, for the actual usable host range (excluding those two), use the Subnet Calculator instead.

Entering an IP address that isn't actually the network address for that prefix, like 192.168.1.5/24, this tool masks the address down to its network boundary first, so the result is still correct, but it means the range shown may not start exactly at the IP you typed.

Assuming a /16 and a /24 cover a similar-sized range, each step down in prefix length doubles the address count, a /16 contains 65,536 addresses versus a /24's 256, an easy-to-miss order-of-magnitude difference when skimming CIDR notation.

Frequently Asked Questions

Does the address range include the network and broadcast address?

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.

What format should I use?

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.