40 years in industrial electrical work and I still found myself Googling "12 AWG to mm²" on job sites more than I'd like to admit. After some general fault in cable deliveries from Europe, that costed us huge amount of money I built a small iOS/Android app to handle it — Unit Converter AWG. I gave it to all engineers at the company to avoid this problem in the future.
First it was only planed to be used for AWG ↔ mm², but i realized that meter, feet, liter, gallons and much more was an issue so I added that to. For me who travels around the world all the time I added a Currency converter that updates everytime you start the app or when you ask for it.
Happy to hear what conversions you wish you had quick access to — always looking to add what's actually useful on the job.
It´s free to use, with ads every third time you change category.