CIDR to IP range converter

How to use the CIDR to IP Range tool

1. Paste CIDR blocks, one per line, such as 192.168.10.0/24.
2. Click “Convert” to see the first and last address, size and netmask.
3. For blocks up to 65,536 addresses, copy or download the full list of IPs.

What CIDR notation means

CIDR (Classless Inter-Domain Routing) writes a network as an address followed by a slash and a prefix length. The prefix says how many leading bits are fixed. In 10.20.0.0/14, the first 14 bits are fixed and the remaining 18 bits can vary, so the block contains 2¹⁸ = 262,144 addresses, from 10.20.0.0 to 10.23.255.255.

The same logic works for IPv6, just with 128 bits instead of 32. A /48, the size many providers give a site, contains 2⁸⁰ addresses, a number so large that the calculator shows it in full rather than rounding.

Where you need this in practice

• Firewall and security group rules: check exactly which addresses a rule like 172.16.0.0/12 really allows.
• Cloud allow-lists: providers publish their ranges as CIDR, and you often need to know whether a particular IP is inside.
• Log analysis and abuse reports: convert a reported block into a range you can search in logs.
• Scanning and inventory: list every address in a /24 to feed a ping sweep or an asset inventory.

If you enter an address with host bits set, such as 192.168.1.10/24, the tool tells you and uses the correct network, 192.168.1.0/24. Many devices silently do the same, which is a common source of confusing firewall rules.

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Frequently asked questions