RPN 28x Calc is a programmable 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
It is a reverse-polish notation (RPN) calculator with a dynamic stack display.
As you add more values to the stack, the display shown on an iPad automatically
expands. To see more lines, simply swipe to scroll. You can also re-order the
levels or modify any of the values on the stack.
"It’s the third RPN calculator I buy for my iPad 2 and the first that makes me happy.
It’s graphically appealing, intuitive and very responsive. I rated it 5 stars."
Advanced commands are available in a secondary panel on iPad or as alternative
button pages on iPhone. The buttons are efficiently grouped into five pages that
you can quickly access by swiping left or right:
- user-defined buttons,
- letters A-Z for typing,
- trigonometric, logarithmic, and data manipulation commands,
- statistics, storage and programming commands
- binary integers, system flags 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 REORD mode, it is possible to rearrange the stack by dragging the rows.
- You can swipe up or down the display to see all levels.
- When you enter a value, you can tap a digit to reposition the cursor.
- Tap on the status indicators in the top of the display to change their state.
- Drag buttons to re-arrange them as you like it (enable that in the settings).
Additionally, on iPad:
- The display automatically resizes to show more than just 4 levels of the stack.
- You can slide the secondary panel out of view or swipe across the panel
to navigate between button pages.
- 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.
- Complex numbers.
- User-defined buttons.
- Interactive button reordering.
- Optional thousand separators.
- Dark Appearance since iPadOS 13 or iOS 13.
- Alternative, dark app icon.
- Haptic feedback on iPhone.
RPN 28x Calc is all you need.
- High precision arithmetics.
- Supports multiple data types: real numbers, complex numbers, binary integers,
or lists, arrays, vectors, matrices, programs, names, and strings.
- Name your own variables; inspect them in the variable viewer (iPad only).
- Create buttons for your programs.
- Use the rich command set to write your own programs.
- View the command history and the results in the log viewer (iPad only).
- Customizable button click & alert volumes.
- Use the same app on iPad or iPhone.
- Use the calculator in iPad multitasking, i.e. in a Slide Over view or in Split View.
- Support for landscape orientation.
- External keyboard support.
- No ads, no tracking, and no rating requests.
- Downloadable user guide with introduction and command reference (PDF).
Plans for future versions (NOT YET SUPPORTED):
- Arithmetic expressions.
- Corrects re-opening the last-used button page.
(Version 3.4 added: complex numbers, a USER page for user-defined buttons, interactive button reordering, and paired statistics commands.)
Ratings and Reviews
Best RPN Calc I’ve tried by far
I’m an old HP-28C junkie. My dad turned me on to HP calculators and RPN in the 80’s. For years I’ve been searching for a decent RPN calc for the iPhone/iPad. Prior to this, all the ones I’ve tried have been severely flawed. On some stack manipulation is wrong or weird — like not entering the current number in the stack twice if I hit enter twice. Infuriating. Alternatively people have made direct emulators of the old HP calculators —as though technology hasn’t gotten better since 1986. This app gets it just right. Everything I loved about my old HP, and everything good about modern tech.
Very nice recent update!
This app has been living in my Home Screen for a long time because of how useful it is; and now it has complex numbers, user defined buttons, and linear regression! Thank you!
I used this calculator in the 80s, it was so far ahead of any other calculators, when I found this app I had tears in my eyes because I loved it so much.
This app is so good I use it everyday
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- Eric Roller
- 2.6 MB
- Requires iOS 12.4 or later.
- Requires iPadOS 12.4 or later.
- iPod touch
- Requires iOS 12.4 or later.
- Requires macOS 11.0 or later and a Mac with Apple M1 chip.
- Age Rating
- © 2013-21 tredje design - Eric Roller
With Family Sharing set up, up to six family members can use this app.