Network boundary
Normalize host IPs
A host input such as 192.168.1.42/24 is converted to the network block 192.168.1.0/24.
Calculate IPv4 CIDR ranges.
Enter an IPv4 CIDR block to normalize the network address, find the first and last IP, and count every address in the range.
Range output
First and last IP
Use the calculated start and end addresses when checking geolocation, allowlists, crawler lists, or reputation data.
Related tools
FAQ
IPv4 CIDR calculator questions
What is a CIDR range?
A CIDR range describes an IPv4 network using an address and prefix length, such as 192.168.1.0/24.
What does this calculator show?
It shows the normalized CIDR block, network address, first IP, last IP, prefix length, and address count.
Can I enter a host IP?
Yes. A host address with a prefix is normalized to the matching network block.