How to Convert Measurements Within Firefox

Working with a web page full of numerical data can be overwhelming, more so if you need these figures to be converted to another unit. You can use online tools, or even just a calculator app, but that would be a nuisance if you’re dealing with massive amounts of figures from a web page.

A better solution would be an add-on for Firefox called Converter. This add-on converts units to other related units with a click of a button. You can either convert an individual measurement or convert all measurements within a page in one go.

First, you’ll need to install the add-on, then restart Firefox.

Upon restarting, you can now navigate to the web page where you have measurements for conversion. In the example below, I wanted to convert a length measurement of 1/8 of an inch.


To convert this to another unit of measurement, you need to highlight and right-click on it. You should see the conversion within the context menu. In the above-mentioned example, 1/8″ is converted to 3.17 mm.

To convert all units in a page, click on the Converter icon (golden apple) on the top right corner of the screen. The icon turns red, indicating that the conversion is done on the page.


The conversions will appear as added text beside the original measurements (see comparison below). To restore the original screen, click on the apple icon again.


If you want to convert one or more measurements that are not on a web page, you can click on the Converter icon and select Custom conversion from the drop down list.

Here, you can type or paste measurements and click on Convert. The conversions should appear in the text box below.


One thing to remember about this add-on is that the free version won’t let you customize what unit of measurement it will convert to. Generally, it uses a common unit that’s closest to the one being converted. In the example above, inches were converted to millimeters, and millimeters to centimeters. To control which units the add-on converts to, you can purchase the Premium version starting at $8.

One exception to this rule are currency conversions. If you want to automatically convert an amount to a default currency, you can do so by going to the Options page and selecting a preferred currency.

Click on the apple icon again and select Options. This should bring you to the Basic tab where you’ll find a drop down list to choose a currency.


This add-on converts almost all units, currencies and even time zones, as long as they are properly formatted using the unit’s symbol ( vs. inch, $ vs. dollars).

Converter is a great tool if you want to immediately see an alternate unit of measurement without leaving a web page. Although the features are limited for the free version, it doesn’t lessen its usefulness.

The great thing about it is it’s ready to convert, and there’s little configuration needed for it to work. The most notable feature is being able to convert all measurements in a page, which is a huge time-saver. That alone cuts the work into half, so this add-on is definitely worth the download.