CIDR Visualizer
A new tool extracted from the codebase.
Last reviewed by the Radiatus Cloud team
CIDR Subnet Calculator
Calculate IP ranges, netmasks, and usable hosts from a CIDR block (e.g. 10.0.0.0/24).
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Turn CIDR notation into a range you can see
CIDR notation like 10.0.0.0/24 is compact but not intuitive: it is not obvious at a glance what the first and last address are, how many hosts fit, or whether two blocks overlap. This tool takes a CIDR block and shows the range it covers, the network and broadcast addresses, the usable host count and the mask, turning the notation into concrete numbers.
Why the prefix length is the whole story
The number after the slash is the count of fixed bits, and every step changes the block size by a factor of two. A /24 is 256 addresses, a /23 is 512, a /25 is 128. Seeing the range expand and contract as the prefix changes builds the intuition that makes subnetting quick: the smaller the prefix number, the bigger the block. The visualiser makes that relationship visible rather than something you compute each time.
Practical for planning and troubleshooting
Whether you are carving an address space into subnets, checking whether a host falls inside a range, or confirming two blocks do not overlap, seeing the actual boundaries prevents the off-by-one errors that CIDR math invites. The calculation runs in your browser with nothing uploaded.
Related tools
- Port Scanner — Check which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
- DNS Misconfiguration — Analyze DNS records (TXT, SPF) for security gaps.
- TLS Compat Tester — Check client-server compatibility for TLS versions.
- Firewall Rule Risk — Evaluate firewall rules for over-permissive exposure.
Frequently Asked Questions
What does the number after the slash mean?
It is the prefix length: the count of leading bits that are fixed for the network. The remaining bits address hosts, so a smaller prefix number means a larger block.
How many hosts are in a /24?
A /24 spans 256 addresses, of which 254 are usable hosts once the network and broadcast addresses are set aside.
What are the network and broadcast addresses?
The first and last addresses in the block. They are reserved, which is why the usable host count is two fewer than the total range.
How do I tell if two CIDR blocks overlap?
Compare their ranges. Seeing the first and last address of each makes an overlap obvious, whereas comparing the notation directly is error-prone.
Is my input uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
Processed locally.
About This Tool
This tool runs entirely in your browser. No data is sent to any server, ensuring complete privacy. Simply use the interface above to get started — no registration or login required.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
Port Scanner
NetworkCheck which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
DNS Misconfiguration
NetworkAnalyze DNS records (TXT, SPF) for security gaps.
TLS Compat Tester
NetworkCheck client-server compatibility for TLS versions.