CIDR to IP Range
Enter a CIDR block and see exactly which addresses it covers.
IPv4 or IPv6; a prefix or mask typed after the address wins.
Convert CIDR Notation to an IP Range
Firewall rules, cloud security groups, VPN settings and allow lists are written as CIDR blocks. This page opens the Subnet Calculator with a block filled in, so you can see where it starts and ends before you open or close access to it.
Examples
| CIDR | Range | Addresses |
|---|---|---|
10.0.0.0/16 | 10.0.0.0 to 10.0.255.255 | 65,536 |
172.16.0.0/12 | 172.16.0.0 to 172.31.255.255 | 1,048,576 |
192.168.1.0/24 | 192.168.1.0 to 192.168.1.255 | 256 |
203.0.113.64/26 | 203.0.113.64 to 203.0.113.127 | 64 |
Block boundaries
A CIDR block always starts at a multiple of its own size. A /26 holds 64 addresses, so it can start at .0, .64, .128 or .192, never at .100. When you type an address inside a block, the calculator finds the start for you, which is a quick way to catch a firewall rule that covers more than intended.
Related tools
For every prefix and its mask, see the subnet mask cheat sheet. For IPv6 blocks, see the IPv6 subnet calculator.