RPN 28x Calc

Math can be fun.

Go to the App Store on iTunes

RPN 28x Calc in action

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 lightRPN 28x Calc iPhone main screenshot darkRPN 28x Calc iPhone X mask

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.

RPN 28x Calc reorder example


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.

Variable viewer of RPN 28x Calc

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).

RPN 28x Calc

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.

Landscape Orientation

When you rotate your device, RPN 28x Calc re-adjusts its layout to fit the available screen area.

Interactive Stack Display

On iPad, the display expands to fill the screen. You can easily scroll and select your entries.

RPN 28x Calc
RPN 28x Calc

iPhone and iPad $6.99
Version 3.5.4 (2580)
01 July 2023
Languages: English

iPadOS, iOS 12 or later.

The dark appearance requires iPadOS or iOS 13.

Go to the App Store on iTunes

Latest News

Version 3.5 adds scientific units, the CONVERT command, upper-tail probability commands, and program debugging using the HALT and SST commands. Also adds the assistant window on iPhone.

Version 3.4 adds complex numbers, paired statistics, linear regression, button reordering and user-defined buttons.

Version 3.3 adds support thousand separators and improves operand colouring.

Version 3.2 improves button responsiveness.

Version 3.1 adds support for a dark appearance for iPadOS or iOS 13.

Version 3.0 introduces programming and matrices and supports iPad multitasking. Also runs on any iPhone with iOS 11 or later.

No Ads

  • No interruptions.
  • RPN 28x Calc does not display ads.
  • There are no rating requests.

Plans for future versions

  • Arithmetic expressions.

Also Note

  • June 28 is Tau Day, celebrating the circle constant τ = 6.283185… (2π).
  • Pi Approximation Day is observed on July 22 (i.e. 22/7).
  • π was introduced as an abbreviation of the Greek word "periphery" (περιφέρεια)