PCalc started on the Mac, but it gained a lot of fame as an iOS app since it's way more flexible than the bundled iOS calculator. With iOS 8, PCalc comes with a Notification Center widget that can save you a lot of time when you need to carry out quick calculations.

The best part? Even if you get the free version of the app, you get the notification center widget, which can effectively replace iOS's built-in calculator completely. You'll still need to open PCalc to use any of the more advanced features, but for any quick calculations, you won't even have to unlock your phone anymore.

What's Good: New notification center widget is handy.

What Sucks: Nothing-this is a utility app that does everything well.

Buy it?: If you're looking for a quick calculator on iOS, check out PCalc. You can get the lite version for free (which lets you unlock advanced features via in-app purchases) or the full version for $9.99 on the App Store.