Web & Networking Tools
Subnet / CIDR Calculator
Calculate subnet masks, host ranges, and usable IPs from CIDR notation.
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What is CIDR Calculator?
CIDR (Classless Inter-Domain Routing) replaces the old classful addressing scheme. This calculator decomposes a CIDR prefix into subnet mask, network ID, broadcast, and usable IP counts for IPv4.
How it works
We parse the IP and prefix-length, compute the bitwise mask, then derive the network, broadcast, first/last usable host, and total address count using standard subnet arithmetic.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.