# SubNet Calc > The sidebar calculates IPv4 subnets. Computes network addresses, broadcast addresses, host ranges, and the number of usable hosts. Canonical page: [https://chrome-stats.com/d/subnet\_calc](https://chrome-stats.com/d/subnet_calc) ## Overview - **ID:** `subnet_calc` - **Platform:** Firefox - **Type:** Firefox add-on - **Status:** Available - **Publisher:** Libor Benes (Dr. B) - **Category:** web-development,privacy-security,search-tools - **Daily users:** 1 - **Version:** 1.0 - **Last updated:** 2025-08-14 - **First published:** 2025-08-11 - **Size:** 18 KB - **Data as of:** 2026-09-26 - **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/subnet_calc/) - **Website:** [https://www.linkedin.com/in/LiborBenes](https://www.linkedin.com/in/LiborBenes) ## Description SubNet Calc is an essential tool for network planning, troubleshooting, and education, combining simplicity, accuracy, and privacy in a compact Firefox sidebar. Designed for network engineers, sysadmins, network analysts, and students to effortlessly calculate IPv4 (not IPv6) subnets. Enter an IPv4 address, a CIDR mask, and the desired number of subnets => get instantly a table with detailed subnet information. Copy results, paste into network documentation or monospaced editors or spreadsheets. Tab-separated output aligns best in monospaced editors (e.g., Notepad++) or Excel; alignment in non-monospaced editors (e.g., Windows Notepad) or WPS Office may vary. Security Prioritization: • Minimal Design. • Offline Operation: Performs all calculations locally, requiring no network access, ensuring privacy - no user data is collected, stored, or transmitted. • Minimal Permissions. • Safe Coding and DOM Manipulation. • Adheres to Moz://a standards for Firefox add-ons, ensuring compatibility and security. • Error Handling. SubNet Calc relies on ipaddr.js, a lightweight, MIT-licensed JavaScript library (version 2.2.0, 13 KB) for parsing and validating IPv4 addresses. ipaddr.js is a part of the add-on's local codebase, no network connections, sourced from https://github.com/whitequark/ipaddr.js. ipaddr.js ensures accurate and safe IP address handling, enabling reliable subnet calculations and input validation. ## Rankings - #104,354 — Overall - #226 — spreadsheet ## Safety - **Risk impact:** Very low risk impact - **Risk likelihood:** Moderate risk likelihood ### Analysis details - This permission has no access or impact on the user's system or data, thus carrying no risk. - This extension website URL may be invalid > Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing). ## Similar extensions and apps - [SubNet Calc for Android](https://chrome-stats.com/d/subnet_calc_android) — 1 users - [SubNet Classer](https://chrome-stats.com/d/subnet_classer) - [IP Calculator](https://chrome-stats.com/d/ip-calc) — 1 users - [IP Subnet Calculator](https://chrome-stats.com/d/ip-subnet-calculator) — 4 users - [Flex Subnetting](https://chrome-stats.com/d/flex-subnetting) — 2 users - [Subnet Calc](https://chrome-stats.com/d/subnet-calc) — 6 users - [IP Subnet](https://chrome-stats.com/d/ip-subnet) — 6 users - [Ip Calculator](https://chrome-stats.com/d/ip-calculator) — 1 users - [CIDR Utils](https://chrome-stats.com/d/cidr-utils) — 1 users - [CIDR Calculator](https://chrome-stats.com/d/cidr-calculator) - [Simple IP Calculator](https://chrome-stats.com/d/simple-ip-calculator) — 20 users, 4.00 / 5 - [HailBytes Engineering Toolkit](https://chrome-stats.com/d/hailbytes-engineering-toolkit) — 1 users, 5.00 / 5 --- Source: [Chrome-Stats](https://chrome-stats.com/d/subnet_calc)