CIDR to IP Range Converter

Turn CIDR blocks into first and last IP, usable hosts and address count, in bulk, with CSV export and subnet mask conversion

CIDR blocks, one per line. An IP with a mask or a range also works

Subnet mask ↔ prefix

Prefix: /24
Subnet mask: 255.255.255.0
Wildcard mask: 0.0.0.255
Addresses: 256
Usable hosts: 254

IPv4 only. Everything runs in your browser. Need details on one block? Try the CIDR Calculator.

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About this tool

The CIDR to IP Range Converter turns CIDR blocks into the addresses they cover. Paste one block or thousands, and each line gets its first and last IP, usable host range, total address count and subnet mask. Rows stay in the order you entered them, so the results line up with your source list, and you can export them as CSV for a spreadsheet or firewall review. It also accepts an IP with a subnet mask (10.1.0.0 255.255.255.0) or a plain range (192.0.2.10-192.0.2.40), and a side panel converts between prefix lengths, subnet masks and wildcard masks. Tick List every IP address to expand the blocks into individual addresses, up to 65,536. Everything runs in your browser, so internal network plans stay on your machine. IPv4 only.

When to use it

→Converting a cloud provider's published IP ranges into start and end addresses
→Preparing a firewall or allowlist review as a spreadsheet
→Importing network ranges into a tool that wants first and last IP columns
→Expanding a small block into a list of individual addresses
→Looking up the subnet mask or wildcard mask for a prefix length

Tips

◆Lines starting with # are ignored, so you can paste commented lists as they are.
◆A block with host bits set, like 10.0.0.5/24, is read as its network, 10.0.0.0/24.
◆To combine or deduplicate overlapping blocks, use CIDR Merge. This tool keeps each row as entered.
◆/31 and /32 have no network or broadcast address, so every address in them counts as usable.

Frequently asked questions

How do I find the IP range of a CIDR block?

The prefix says how many leading bits are fixed. The first IP has all remaining bits set to 0, and the last has them set to 1. So 192.168.1.0/29 keeps 29 bits fixed, leaves 3 free (8 addresses), and runs from 192.168.1.0 to 192.168.1.7.

How many IP addresses are in a CIDR block?

2 to the power of (32 minus the prefix). A /24 has 256, a /16 has 65,536 and a /8 has 16,777,216. Usually two are reserved for the network and broadcast addresses, and cloud providers reserve more.

What's a wildcard mask?

A subnet mask with its bits flipped, so 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF configuration use them.

Does it support IPv6?

Not yet. It handles IPv4 only.