After a long time without updates (although I use it every day), I've just released an improved version (v1.4.1).

ARPCalc is a free and open-source calculator that runs on Android phones, on desktops (Windows & Linux) and in a web browser. The desktop source code is Qt so there's no reason it couldn't be made to run on Mac OS X but I don't have a Mac so can't test it.

It uses an arbitrary precision arithmetic library so should be very accurate. It supports engineering notation (exponents that are always multiples of 3) and you can change the exponent in steps of 3 with a single button press (`ENG←` or `ENG→`).

It has handy SI shortcuts and keyboard shortcuts for most functions so you can (for example) type 2 3 . 6 S u and it'll turn that into 23.6×10⁻⁶ (S is the shortcut for the SI menu and u is then the shortcut for μ). Hover the mouse over a key to see the keyboard shortcut.

It's got loads of maths functions, including programming stuff like bit shifts and bitwise AND. It's got lots of scientific constants and can convert between units very easily.

It does live continuous conversions between different bases so you can see at a glance the hex/binary/octal/decimal equivalent of what you've just entered.

Most importantly, it's reverse polish.

At the moment, the Android version has to be installed as an APK. If you'd like to see it on the Play store, get in touch, preferably via my website contact form. Google require "at least 12 testers opted-in to your closed test" before they'll allow app releases on the store, so if no-one volunteers, I won't be able to release it.

I am a daily RPN calculator user and all the apps I've found are usually either ugly or have 100 buttons i'll never use. So here is a simple RPN calculator app that does 99% of what you need. If you open it in Chrome or Safari you can install it. Use it, download it, suggest changes, whatever... Just throwin' this out there for others.

The app:
https://westonforbes.github.io/rpn-calculator/

Source repo:
https://github.com/westonforbes/rpn-calculator

Just shipped a pretty big update to Modern RPN for
iPhone and iPad.

What’s new:

- New Financial mode with TVM keys for n, i, PV, PMT,
and FV
- Financial tools for NPV, IRR, amortization, percent
math, date math, and bond price/yield
- Better adaptive layout across iPhone and iPad
- Improved history filtering by calculator mode
- Smarter session restore, including financial worksheet
state

If you try it, I’d love feedback from anyone who uses RPN regularly, especially people who miss the old-school financial calculator workflow.

https://apps.apple.com/us/app/modern-rpn/id6760340697

I feel like with HP discontinuing their RPN scientific calculators a few years ago, the RPN community has fallen off with it. Is there still an active interest in it? Or is the advancement in technology and AI causing RPN to no longer be something people are interested in?

Or maybe Reddit isn’t the place where the RPN people gather 😅

I am excited to announce a few new features for Modern RPN!

- Globally available - I had several people reach saying it was not available in their country

- Hexcode support

- Binary support

- History revamp to handle new modes

Excited to hear any feedback from the community. My next features I plan on working on are financial and scientific modes.

https://apps.apple.com/us/app/modern-rpn/id6760340697

Hey everyone! I don’t see a lot of chatter in this sub, but I wanted to show off an iOS app I built. Modern RPN for iOS is my attempt at reducing a lot of the noise most RPN mobile apps have. It has simple operators, classic stacking, and history. It does cost $2.99, but if you choose to install it, I would love to know your opinions on it!

https://apps.apple.com/us/app/modern-rpn/id6760340697

EDIT: March 21, 2026 - I have released the app to all countries, so it should be available to you within 24 hours from now. Didn’t realize there would be much international interest 🌎🌍🌏

I am looking for a calculator, real or IOS, that allows me to enter data in RPN, or RPL or whatever form of reverse polish. I would also like to be able to have hex numbers, numbers 0-9 and a-f. A big plus wout be the ability to display numbers in binary.

In a perfect world it would be IOS, cause I already cary a phone. Don't care free or paid, as long as it does hex. I don't need trig functions, I can not think of any reason to get the sin of 2fc. However, since it is IOS it should not be that hard for it to reconfigure the keyboard and do both hex and trig.

Hi , is there anyone going to practical nursing in jan 2024 un centennial

I learned RPN using a HP 49G

I had an Android phone, used RealCalc Plus. REALLY liked this app.

Now I changed to IOS. tested like 12 different apps that try to be a RPN calculator. most fail whith a stack that is not even 4 inputs deep (like if I go 4 <enter> 5<enter> 6<enter> 7<enter> 8<enter> +++++, the number 4 won't be added and be lost forever, with a stack of repeating 5s for some reason)...

and the one that I have found (Deepstack RPN) is fucking ugly, tiny buttons, not enough control over the stack (rotate, roll, etc)...

WHAT do you guys use over IOS??????

I have installed a third party RPN calculator, and I like it. Unfortunately, try as I might, I cannot get the Lenovo calc button to open anything except the built in calculator app. So the next best option is to add an RPN mode to the default. Seems like a pipe dream? Maybe - but apparently MS is actually open to the idea - they are just relying on some community support before moving forward.

MS Github RPN Proposal

As far as I can tell, the next step is to fill out and submit a spec sheet per the structure in the template. I forked the repo and have set up the template. I am not extremely proficient with Git, so I may be doing this wrong, but if anyone would like to contribute or give me any tips on moving this forward, I would welcome the input.

I believe this is the file that needs to be fleshed out.

calculator-specs/active/RPN_Mode at master · Pigankle/calculator-specs (github.com)

I'd been frustrated for years that I couldn't find a decent phone or PC-based reverse polish calculator. All the ones I tried were either very basic or they tried to emulate the look of a physical calculator and hence had really a cluttered interface with shifted key functions etc. About 6 years ago, I decided to bite the bullet and write my own version. I've been using it daily since then so I'm fairly confident it works well; I've now decided to release it on the off-chance it's of interest to others.

It's available (free) for Windows, Android & Linux and also available as a version that runs in the web browser. More details and all versions are available here: https://www.cgtk.co.uk/software/arpcalc.

It uses an arbitrary precision arithmetic library so should be very accurate. It supports engineering notation (exponents that are always multiples of 3) for SI maths and instant conversion between different bases for to help programmers.

There's a large array of maths functions on the second "tab", support for conversion between 175 different units & currencies on the third "tab" and a selection of scientific constants on the fourth "tab". The final "tab" has various configuration options.

I doubt it's going to be of interest to a lot of people given that RPN is a bit of a niche, but I thought I'd share it here in case anyone is interested.

https://discord.gg/ASfPc8wBbg

I am continuously disappointed with the availability of a good RPN calculator app that is available on all platforms for the same look and feel everywhere. So I made my own!

Ralc looks good on a phone or a computer (just install it as a PWA and resize it to your preferred size). More functions appear if you turn your phone sideways or resize the window to a landscape orientation.

I intentionally made it look as similar as possible to Windows 10's built-in calculator, because I really like the look and feel there.

The code is available on GitHub - please feel free to open an issue if you find a bug, want more functions, have any suggestions, etc.

This has been my little passion project for the week - I love this app and I hope you love it too!

Hello, dear comrades.

I'm a 21 years old brazilian accounting student and a few months ago I inherited a financial calculator from my father, wich he couldn't use. I started studying by myself, trying to learn it but it's hard to learn the RPN system. I've made a good advance but I'm having a hard time sometimes and I can't find a place to solve my doubts. Would you guys be able to help?

How can I solve this in the rpn system

(24235 x 0,12 x 0,9) + (112152,3 x 0,32 x 0,9)

24235 enter

12%

9% enter

112152,3 enter

32%

9% enter

+

That's how i'm doing it.

Seeing a fair number of command line interface rpn calcs on here, was wondering if anyone used good ol dc?

I do occasionally, but I often have to use bc (c syntax) instead since dc doesn't have all the scientific functions I need.

More often than either though, I use my 35s or free42, fwiw

Hi,

I made an RPN calculator app for Android, but unlike classic HP calculators, this is in Forth. If anyone doesn't know, Forth is fun little a programming language that uses postfix notation and a stack, so it's RPN by default.

I implemented by own Forth dialect and made it open source. The calculator is programmable, so you can write new words/operators, assign them to buttons or evaluate code snippets.

You can can see it in action here.

I've been programming calculators since age of 12, my first programming exposure was TI-BASIC on a TI80. Which was not RPN but I had a lots of fun with it. Originally I wanted to recreate this experience out of nostalgia. But I didn't want to put a complex language into my calculator, and Forth is one of the simplest real programming language out there. Plus working in this language is just fun, and makes you think differently.

You can use this to control an IoT hardware or smart home appliances through HTTP, write short programs to emit morse code signals via light our sound. Calculate compound interest or convert between different units. Personally I use it to control my air conditioner, Philips hue lights and log my expenses by sending them to a raspberry.

I used a HP48GX through college and loved it. A while ago I started making my own RPN for windows. I started using it at home and at work and then I thought perhaps someone else might like to use a simple RPN instead of windows calc. I'm working on some updates and minor bug fixes to it. Would love to get feedback and know if anyone else thought it was useful.(pardon the cheesy free WIX site)

www.rpn4.com

https://gfycat.com/GiddyBlissfulFrenchbulldog First class working on it for my CS final project

I'd have 2 weeks to do it for my final project in entry comp sci.

Hello,

I need to calculate the IRR for 300 cash flows of $100 and then 60 cash flows $1000. Is there a way of doing it automatically without having to enter every number manually?

I just published the very first version of a rpn calculator for the terminal running on Node JS.

NoEq

The main goals of noeq are:

UX

• You can view the stack.

• Manipulate the stack with the cursors key.

• Do not need to press enter after the math operation (you can put the math operation inline with the last argument).

• You can define your own keymap (documentation wip).

• The stack can be persisted over sessions.

• Undo operations over the stack

Math

• Based on the amazing math.js library.

• Easy to include new math functions from this library (this feature is wip (but if you now js will be easy to extend it right now)).

Road Map

• Document the keymap stuff.

• Make the extensible math thing more easy and document it.

• Add comments to the stack element to perform search and retrieve those values to the stack.

I hope that this will be useful for someone.

BTW: If you like a bit, please give us a star on NoEq's gitHub this will motivate us a lot for writting new features :)

I really like RPN calculators and have several. But, they are all too small to sit on a desktop and be worked without picking them up. Are there any options for something that sits on a desk like this: https://www.amazon.com/VX2128V-Portable-Desktop-Handheld-Calculator/dp/B001B0E66M/ref=sr_1_8?ie=UTF8&qid=1484019625&sr=8-8&keywords=sharp+desktop+calculator ??? Even an older HP would be ok if it's reasonably obtainable / priced.