One of my favorite calculator apps to use when I had an iphone. Think this is the cheapest it's ever been.
PCalc is the powerful choice for scientists, engineers, students, programmers, or indeed anybody looking for a feature rich calculator. It includes an optional RPN mode and multi-line display, a choice of button layouts, an extensive set of unit conversions and constants, a paper tape, multiple undo and redo, engineering and scientific notation, as well as support for hexadecimal, octal, and binary calculations.
Includes an Apple Watch app, so you can calculate on your wrist!
What's New
Improved the iPhone X support a little bit more.
Good calculator app.