How to Do Math and Conversions in Firefox's Address Bar

This article explains how to transform the Mozilla Firefox address bar into an instant calculator and unit converter. By enabling two built-in hidden features in Firefox's advanced configuration settings, or by activating search engine suggestions, you can solve mathematical equations and convert measurements directly in the URL bar without pressing the Enter key or loading a webpage.

Enable the Built-in Calculator

Firefox includes a native calculator that is disabled by default. You can turn it on through the advanced configuration page.

  1. Open Firefox, type about:config into the address bar, and press Enter.
  2. Click the Accept the Risk and Continue button.
  3. In the "Search preference name" box, type browser.urlbar.suggest.calculator.
  4. Click the Toggle button (the two-way arrow icon) on the right side of the screen to change its value from false to true.

How to use it: Type any mathematical equation into the address bar, such as 256 * 14 or (50 + 30) / 4. The answer will immediately appear in the drop-down menu with a calculator icon. Clicking the result copies the answer to your clipboard.

Enable the Built-in Unit Converter

Like the calculator, Firefox has a native unit converter that must be manually enabled.

  1. Navigate to about:config in the Firefox address bar.
  2. In the search box, type browser.urlbar.unitConversion.enabled.
  3. Click the Toggle button on the right to change the value from false to true.

How to use it: Type your conversion query into the address bar using "in" or "to" between the units. For example, type 10 km to miles, 75 f in c, or 50 kg to lbs. The converted value will appear instantly in the drop-down menu. Click the result to copy it to your clipboard.

The built-in converter currently supports:

  • Temperature: Celsius, Fahrenheit, Kelvin
  • Length: Meters, kilometers, miles, feet, inches, yards, millimeters, centimeters
  • Mass: Kilograms, grams, milligrams, tons, pounds, ounces
  • Speed: Kilometers per hour, miles per hour, meters per second, knots
  • Angles: Degrees, radians, gradians
  • Timezones: Type time in [location] or 10am EST to PST

Alternative Method: Use Search Engine Suggestions

If you prefer not to edit advanced configuration settings, you can use your default search engine to display answers directly in the address bar.

  1. Click the Menu button (three horizontal lines) in the top-right corner of Firefox and select Settings.
  2. Click on Search in the left-hand menu.
  3. Ensure your default search engine is set to Google, Bing, or DuckDuckGo.
  4. Scroll down to the "Search Suggestions" section and check the box for Provide search suggestions.
  5. Check the box for Show search suggestions in address bar results.

When you type a calculation or conversion into the address bar, Firefox will fetch the answer from your search engine and display it in the drop-down list preceded by an = sign. Note that unlike the about:config method, this method requires an active internet connection and sends your keystrokes to your chosen search engine.