This great add-on for Firefox will convert units, timezones and currencies on any web page — and you also get a shopping assistant finding the best prices for you! (Currency conversions and the shopping assistant are disabled by default, but you can enable and disable them at any time.)
If you do a lot of work with numbers, this will be a great add-on for you to try. It really does a great job – plain and simple.
The best part about this add-on is you don’t have to choose the units from drop-downs — Converter understands the units and converts them in place. Convert either a single measurement (select and right click), or the entire page (click the icon).
Want to pick it up? You can get the Converter add-on for Firefox from the Firefox Add-ons website.