RPN 28x Calc

Math can be fun.

High Precision Arithmetics

Supports numbers with up to 38 significant digits.

Multiple Data Types

Real and complex numbers, binary integers, lists, arrays or vectors, matrices, names, strings and programs.

Scientific Units

There is a catalogue of 147 pre-defined scientific units and constants. Custom units can be added through variables.

RPN 28x Calc

RPN 28x Calc is a programmable scientific calculator for iPadOS and iOS. It uses reverse-polish notation (RPN) for its operation and features a unique dynamic stack display.

You can operate with real numbers, complex numbers, binary integers, names, scientific units, strings, lists, arrays or matrices, and you can write programs to expand the functionality to your needs.

Advanced commands can be accessed via command pages, which open in a secondary panel (on iPad) or replace the regular panel (on iPhone). You can swipe across the button panels to navigate between the pages. On the user page, you can add your own buttons.

iPhone and iPad

RPN 28x Calc is a universal app which can run on iPhone and iPad, whichever size you have, as long as you have version 11 or later of iOS (or iPadOS).

It supports a light and dark mode (for iPadOS/iOS 13) as well as two colour themes: the default "Black & Grey" theme and "Brown & Sand" which you can select on in the settings (any iPadOS or iOS version). Check out the screen shots to see more examples.

RPN 28x Calc iPhone main screenshot light

RPN 28x Calc iPhone main screenshot dark

Dynamic Stack

On iPhone, you can swipe the stack display down to see values on lower stack levels.

On iPad, the display automatically expands as you add more values to the stack. Once fully expanded, you can swipe down to see values on lower stack levels.

You can also re-order the levels or modify any of the values on the stack.

Programmable

Use the rich command set to write your own programs.

User-Defined Buttons

Create your own buttons for easy access to your own programs (stored in variables).

iPad Multitasking

You can use the calculator in Slide Over or Split View alongside other apps on an iPad.

Scientific Units Catalogue

You can browse all predefined scientific units and constants in the assistant window.

Variable Viewer

You can view all variables in the assistant window. To make a variable available to a command, simply select it in the window and issue the command. Double-tap a variable to edit it.

For variables that contain programs, feel free to create a button with which you can easily execute it.

Command & Results History

Select "Log" to display your command history. To place a value back onto the stack, double-tap it. Swipe upwards to reveal a panel of action buttons, i.e. to delete entries or to share the log.

Button Reordering

Create your own button layouts. Long-press to move a buttons.

Work With Operands

Tap an operand in the display to select it. Then issue a command which will use your selected operand.

User Guide

From the (i)nfo menu within the app, you can download the user guide with an introduction and a command reference.

Download PDF

See below for older versions.

Scientific Units

You can make use of 147 pre-defined scientific units and elementary physical constants in your calculations. Additionally, you can define variables to create your own units or constants.

All units, including the Imperial units, are derived from the seven SI base units. plus there is an eighth, user-defined base unit for custom needs. Units can be combined and converted (if they are compatible). SI prefixes can be used to scale the units. Example: "1 km" vs. "1000 m".

In the assistant window, you can browse the catalogue of scientific units. They are also listed in the Uer Guide (PDF).

Multiple Undos

You can restore previous stacks with the UNDO command. LAST restores the most recently used operands. With COMMAND, you can get back the most recently typed input.