CIDR / IP Range Expander
Enter a CIDR block or start-end range to list every IPv4 address it contains, plus network, broadcast and host bounds — all computed in your browser.
Updated
- Network / start
- 192.168.1.0
- Broadcast / end
- 192.168.1.7
- First host
- 192.168.1.1
- Last host
- 192.168.1.6
- Total addresses
- 8
How to use CIDR / IP Range Expander
The CIDR / IP Range Expander turns a subnet or address range into the concrete list of IPv4 addresses it contains, instantly in your browser. Enter a CIDR block like 192.168.1.0/24, a start-to-end range, or even a shorthand range, and the tool reports the network and broadcast addresses, the first and last usable hosts, the total address count, and a copyable list of every address. It saves you from error-prone mental binary maths when you need to populate a firewall rule, a monitoring target list, or a spreadsheet of addresses to scan or document.
- Enter a CIDR block, a range, or a single address.
- Review the network, broadcast and usable host bounds.
- Check the total address count for the block.
- Copy the generated address list.
- Paste it into your firewall, monitor or spreadsheet.
Your data never leaves your device — 100% private processing.
CIDR notation and ranges explained
CIDR (Classless Inter-Domain Routing) notation writes a block of addresses as a base address followed by a slash and a prefix length, such as /24. The prefix length is the number of leading bits that are fixed for the whole block; the remaining bits vary across the addresses it contains. A /24 fixes 24 bits and leaves 8 bits free, giving 256 addresses (2 to the power of 32 minus 24). Smaller prefix numbers mean bigger blocks: a /16 holds 65,536 addresses, a /30 holds just four. This tool also accepts explicit ranges, either fully dotted like 10.0.0.1-10.0.0.50 or with a shorthand end such as 10.0.0.1-50, and a single address on its own. Whatever you enter, it computes the same set of bounds so the output is consistent.
| Prefix | Addresses | Usable hosts |
|---|---|---|
| /30 | 4 | 2 |
| /29 | 8 | 6 |
| /24 | 256 | 254 |
| /16 | 65,536 | 65,534 |
Network, broadcast and usable hosts
Within a normal subnet, the first and last addresses have special roles. The first address is the network address, which identifies the subnet itself, and the last is the broadcast address, used to reach every host on the segment at once. Neither is normally assigned to a device, so the usable host range runs from the second address to the second-to-last. That is why a /24 with 256 total addresses provides 254 usable hosts. For very small blocks the picture changes: a /31 (two addresses) is used for point-to-point links where both addresses are usable, and a /32 is a single host. To keep the page fast, the printable list is capped at 1024 entries, but the reported total always reflects the full block so you know exactly how large it is.
Worked examples
Expand a /29
Inputs: 192.168.1.0/29
Result: 8 addresses · hosts .1–.6
Shorthand range
Inputs: 10.0.0.1-5
Result: 10.0.0.1 … 10.0.0.5
Glossary
- CIDR
- Classless Inter-Domain Routing — a way to express a block of IP addresses as base/prefix.
- Prefix length
- The number of fixed leading bits in a CIDR block, written after the slash.
- Network address
- The first address in a subnet, identifying the subnet itself rather than a host.
- Broadcast address
- The last address in a subnet, used to address all hosts on it at once.
- Usable hosts
- The addresses in a subnet that can be assigned to devices, excluding network and broadcast.
Related reading
Frequently Asked Questions
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Why use CIDR / IP Range Expander?
- Convert a CIDR block or range into an explicit address list
- Accepts CIDR, dotted ranges and shorthand last-octet ranges
- Shows network, broadcast, first host, last host and total count
- Copyable list ready to paste into configs or spreadsheets
- Runs client-side — your addresses never leave the browser
Common use cases
- Build a firewall or allow-list rule from a subnet
- Generate a list of monitoring or scan targets
- Document every address in an allocation for an audit
- Check how many usable hosts a given prefix provides
- Translate a CIDR block into individual DHCP reservations
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