Android: Unit conversion apps are a bit of a bore, but Convert Everything takes the concept to a whole new level. It's probably the most complete unit conversion tool we've seen, and can convert everything from length measurements and currency to clothing/shoe sizes to resistance and magnetomotive force.
Of course, on most Android phones you can ask Google Now or Google Search to do these unit conversions for you, but Convert Everything does it in a snap, and features even more conversion methods than Google offers. At some point, Google will shunt you off to another conversion tool to handle it, while Convert Anything will do it all right there on your device.
The app is probably ideal for students or anyone who frequently has to perform quick conversions and needs a good tool to do it. Convert Everything is free, and works on Android phones running 2.2+. Hit the link below to grab it from Google Play.
Convert Everything (Free) [Google Play]