iPad Screenshots


RPN 28x Calc is a scientific calculator with a pleasingly classic look. Despite its nostalgic appearance, it offers a modern and intuitive user experience, allowing you to interact with your operands by touching them in the display.

It is a reverse-polish notation (RPN) calculator with a dynamic stack display that automatically expands such that you can see up to 16 levels at a time. You can easily scroll through the stack to reveal additional levels, when present.

Advanced commands are available in the secondary panel. The buttons are efficiently grouped into four pages that you can quickly access by swiping left or right:

- letters A-Z for typing,
- trigonometric, logarithmic, and variable commands,
- statistics, arrays, lists, and string manipulation,
- binary numbers and boolean logic.

This is why RPN 28x Calc is unique in its class:

- You can tap a row to select it and issue commands for the selected level.
- In EDIT mode, it is possible to rearrange the operands.
- The display automatically resizes to show up to 16 levels of the stack.
- You can swipe up or down the display to see more than 16 levels.
- You can slide the secondary panel out of view or swipe across the panel
to navigate between button pages.
- When you enter a value, you can tap a digit to reposition the cursor.


- You can browse all variables and your command history in a separate viewer.
- Select a variable in the viewer to make it available as an argument to
variable-related commands in the calculator.
- Double-tap a variable in the viewer to edit it.
- Double-tap an entry in the command log to place it back onto the stack.
- Tap on the status indicators in the top of the display to change their state.

RPN 28x Calc is all you need.

- High precision arithmetics.
- Supports multiple data types: real numbers, binary numbers, lists, arrays
or vectors, names, and strings.
- Retina-resolution graphics.
- Name your own variables; inspect them in the variable viewer.
- View the command history and the results in the log viewer.
- Customizable button click & alert volumes.
- Support for landscape orientation.
- External keyboard support.
- No ads, no rating requests.
- Downloadable user guide with introduction and command reference (PDF).

Too quick? This is shown in the app preview video:

- The variable viewer is revealed.
- All four button pages in the secondary panel are presented.
- The contents of the variable 'LIST' is placed on the stack (RCL).
- The number PI on level two is selected, then removed (DROP).
- The list is unwrapped with the LIST-> command.
- Scrolling of the stack is demonstrated.
- The list size value (19) is removed from the stack (DROP).
- The entry on level 13 is changed from 0.9 to 0.5 (MODIFY).
- The data and command log is revealed.
- All values are added (+).
- The side panel is collapsed and the log window expands.

Plans for future versions (NOT YET SUPPORTED):
- Better iPad Pro support.
- User-definable buttons.
- Support for programs.
- Complex numbers.
- Matrices, i.e. arrays within arrays.
- Arithmetic expressions.

What's New

Version 2.2.1

- Added an option reduce motion in the startup animation.
- Fixed: The Copy & Paste Shortcut bar will no longer appear, even when Bluetooth is enabled.

Version 2.2

- The display status indicators for LC, SHIFT, (2π), HEX-DEC-OCT-BIN, and STD-SCI-FIX-ENG are now active! You can tap on them to change their state.
- Adjustments for iOS 9.
- Updated icon and launch animation.

RPN 28x Calc will not prompt you for a review. Nevertheless, if you enjoy using the app, please be a star and take a moment to leave a mathematically correct review. To get to the App Store quickly, you can use the "Rate This App" item in the (i)nfo menu from within RPN 28x Calc.

Ratings and Reviews

4.2 out of 5

5 Ratings

5 Ratings

Powerful & Easy to Use


If you're comfortable with rpn (reverse polish notation), this is an excellent app. It may be overkill for the average joe, but this is reminiscent of my 48GX calculator, used back in engineering school, without the graphics/plotting interface.

If you're not accustomed to rpn calculators, but are in a technical field, now is the time to consider learning. There's no huge learning curve here; just a different way of entering your numbers. It seems awkward at first, but for large formula hacking, rpn is the way to go, making short work of the most complicated calculations!

This one is more expandable than at first meets the eye, offering all the basic necessities for solid number crunching.

FANTASTIC - this is the only way...

Blue Pine

I can't really run a "normal" calculator because I've always used RPN, and it makes sense. Nothing else makes sense. So even when I got my iPad, I still pulled out my RPN calculator to add 2+2. Then I found this app! So happy, so perfect! I can hardly believe it - this is everything I want or need. PERFECTION!

I'm so grateful I found this one because RPN is the only way to go, and this one works without the problems and weirdness of the other RPN app I tried. That other one was several times the price, and turned out to be a somewhat bizarre and terribly problematic nightmare, in my opinion. I deleted it very quickly.

This one works. And, it is well designed, it has GREAT documentation, and I absolutely love it. This app is turning my physical RPN calculator into a museum piece lol.

This is a great app, and they've made me a happy camper :)

Just like an HP28S

The wild card 205

I used an HP 28S when I went to engineering school and I loved it. This app works almost exactly like my old HP. I love this app.


Eric Roller
3.6 MB
Requires iOS 7.1 or later. Compatible with iPad.
Age Rating
Rated 4+
© 2013-15 tredje design - Eric Roller


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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