As soon as you start typing the unit a list of candidates appears and you can select it from the list, so you never have to type more than the first few letters... I find this much more convenient than hunting through long lists of possible candidates after having selected from another long list of categories. I have yet to find a unit it doesn't know or a conversion it cannot perform! Simple, fast and accurate, this is a great example of app design. Of course you do have to know the unit beforehand, but that is hardly a limitation in the real world.