Best Calculator Apps for iPhone

PCalc

PCalc is an incredibly powerful calculator app that is designed with professional users in mind. If you are a scientists, engineer, programmer or student in one of these fields; PCalc is the app you're looking for. 

You can turn on an optional RPN mode if you need to use this feature. The multi-line display makes it easy to see your calculations and history as you work through multiple problems or parts of problems. 

It's possible to choose the button layout that fits you best and there are also plenty of unit conversions and constants that you can work with. 

The app includes support for engineering and scientific notation. It also supports hexadecimal, octal, and binary calculations.