Subnet / CIDR calculator
IPv4 network, mask, broadcast, and usable hosts from CIDR.
Runs in this tab. The file stays here.
This runs in your browser. Nothing is uploaded.
About Subnet / CIDR calculator
Calculate IPv4 network address, subnet mask, broadcast, and usable hosts from a CIDR — offline.
CIDR arithmetic shows up whenever you carve a VPC, write a firewall rule, or explain why /24 is not /16. This page takes an IPv4 address plus prefix length and derives network, mask, broadcast, and usable host counts without a cloud console.
IPv6 is intentionally out of scope for this version — different bit width, different UX. Paste or type something like 192.168.1.10/24 and read the derived fields. No WHOIS, no live probe of the network.
Chmod is Unix file modes. API tester hits HTTP endpoints you choose. Ohm’s law is electronics. This tool stays IPv4 subnet math.
How to use Subnet / CIDR calculator
- 1Enter an IPv4 address and prefix length (CIDR).
- 2Read network, mask, broadcast, and host capacity.
- 3Copy values into your infra docs or security group rules.
What it won't do
- IPv4 only.
- No IPAM inventory or cloud account sync.
Common questions
Does the subnet calculator support IPv6?
Not yet. IPv4 CIDR only in this version.
Are usable hosts excluding network and broadcast?
Yes for ordinary subnets where those addresses are reserved. Point-to-point edge cases follow the usual teaching formulas the UI labels.
Does it scan or contact the network?
No. Pure arithmetic on the address you typed.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation