CIDR / Subnet Calculator

Break down any IPv4 CIDR block into network and broadcast addresses, usable host range, host count, and netmask. Runs entirely in your browser.

Documentation (Markdown)

Networking

Documentation

CIDR Calculator

Analyze a single IPv4 CIDR block: network, broadcast, mask, and host range.

CIDR block

Prefix length/24

Runs locally. Nothing is sent to any server.

API endpointGEThttps://ronutz.com/api/v1/cidrDocumented, not served. Opens the specification.

What this page needs

Runs in your browserJavaScript + CSSAPI-ready

This tool computes entirely on your device, so nothing you type is sent anywhere. That local computation needs JavaScript; CSS is used for layout and theming.

This tool is built to also work over an HTTP API. Processing is currently off, so the API is documented but not served; when it is switched on, you will be able to call it without a browser.

JavaScript is off, so the live tool will not run.You can still read this page's explanation, open the Markdown reference and the Learn article, and follow the sources below. Turn JavaScript on to use the interactive tool.