This add-on automatically translates all sites from American units to International System of units (SI/Metric), adding converted unit in brackets behind USC units. Example: 10 feet 🠚 10 feet【𝟯 𝗺】 Convenient for Amazon shopping, cooking, etc. Inch, Feet, Yard, Mile -> Metre (Meter) Pound, Ounce, Stone -> Kilogram Gallon, Quart, Pint, Fluid Ounces, Cups -> Litre (Liter) mpg -> L/100 km mph -> km/h Fahrenheit -> Celsius Area conversion for ft, yd, in, mi, both as "sq. ft" and "ft²" (must not be superscript); the same is for volume conversion. Toolbar button to turn ON/OFF globally Shortcut Alt+M to force conversion (You can keep extension off, and only press the shortcut when you'd like page converted) Don't forget to check Options page. Not working on a specific site? Have a suggestion for improvement? Send me an email with details. Now open source, contribute to code at https://github.com/m1l/Everything-Metric-Firefox or contribute with a coffee for the developer at https://paypal.me/milospa Permission to read page data is required to be able to modify page text to add metric units. Permission to storage is required to save settings.