Premium Member Database last update: Wednesday, October 26, 2016 6:02:56 GMT-0700

Create CIDR Ranges from Network Blocks

Our CIDR Calculator takes a starting network address and the number of hosts assigned to the address block and creates the fewest number of legal subnets or supernets within the assigned network block. Correct output is produced only when a legal network address and number of hosts are entered into the form. For example: if you have a block of networks comprising the range -, your network address or Starting IP is and your number of hosts is 9175040.

Entering a Starting IP of and 9175040 as the Number of Hosts will produce CIDR output of,,,,,,,,, Give it a try.
Starting IP:
Number of Hosts:

This calculator is currently free to use, but will soon become part of our members only section. Accessing this form remotely is not allowed and may lead to the permanent blocking of your access to this website.