I'm of the belief that most of the utilities you'll ever need already come installed on your iPhone. But if you'd like to add to your collection, the smart way to go may be to add apps that contain multiple utilities in one collection-- and are your best bets here.

One app that will definitely improve upon what comes with the iPhone and iPod touch is , which offers advanced functions and useful conversion and constant features. Grab it if you expect your calculation needs to go beyond what the iPhone's built-in tool is capable of.

Speaking of conversions, there are a pair of apps that have their share of fans in the offices. and both feature excellent controls for converting one measurement to another.