RPN vs WP 31s
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app meticulously simulates a 1973 scientific calculator, offering an authentic vintage experience with advanced features. It includes a paper tape printer, complex number calculations, and enhanced statistical functions. Users can customize its appearance and even use it as a timer or chess clock.
- Photo-realistic HP-45 simulation
- Animated keys with feedback
- Full HP-45 function implementation
- Paper tape printer with export
- Complex number calculations
- Enhanced statistical functions
- Timer and chess clock modes
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RPN-45 HD is a complete simulation of the scientific hand-held calculator HP-45 from 1973. Processing times and behavior have been carefully modelled after the original. Switch to the "Super-45" mode and watch the HP-45 do things never seen before. Features: • Photo-realistic look based on an existing device • Animated keys with adjustable click sound and visual feedback • All functions and operations of the HP-45 fully implemented • Supports "secret" timer. Use it as 12/100-hours timer or even as a chess clock. • Optional hyperbolic functions • Simulation of the HP-45's computation times (optional) • Correct wrong number entries by swiping left across the display • Cut/copy/paste display value • "Live" display of stack and all memory registers (in landscape mode) • Built-in manual • 30 selectable background images, even add your own • HP-91-like paper tape printer: - Supports MAN, ALL, and NORM modes - Quickly insert arbitrary text - Delete any line - Send tape via E-Mail or to any AirPrint-capable printer - Ribbon color black or blue - Optionally print negative results in red - Print stack and registers • Supports external hardware keyboard Turn on "Super-45" and enjoy a super-charged HP-45: • Complex numbers: available for almost all operations and functions • More memory: twice the number of memory registers. • "Continuous" stack and memory registers • Improved functions: - Raise any number to any power - Factorial of any number, incl. complex - Logarithm and square root of negative numbers - Preset timer with the iPad's real time - Chess clock mode • New functions: - Solve linear equations in two or three unknowns - Find the roots of quadratic and cubic equations - Statistics: normal distribution and correlation coefficient of paired variables - Linear regression, combinations, permutations - Logarithm to any base, incl. complex - Integer and fractional parts - Display rounding - Random numbers in a given range - Day of the week for any date between Jan 1, 0001 and Dec 31, 9999 - Easter date for any year between 1583 and 4099 - Support for Julian dates - Number of days between any two dates - Last Stack - Convert display value to hexadecimal - Percentage of sum - Register arithmetic includes sum registers and LAST x - Clear all registers - Backup registers in a protected area • Enhanced user interface: - Visual indicators for prefix keys and angular modes - Small values switch to scientific notation if required - Localized decimal point - Thousand's separator For more information and sample calculations visit cuveesoft.ch/rpn45/en WHAT USERS SAID: "A great simulation of the HP-45. Beautifully made, with a lot of attention to small details." "This is by far the best RPN calculator available for the iPad!" "This is one of the most accurate but also nicest looking emulators I have come across for the HP-45, or any vintage HP calculator for that matter." "This is exactly what I've been searching. My HP 45 packed up some time ago. Thank you so much!"
WP 31s
This app emulates a classic RPN scientific calculator, offering a rich function set for daily use with a simplified interface. It's based on the more complex WP 34s but is designed for easier operation.
- RPN scientific calculator emulation
- Rich function set
- Simplified, less cluttered keyboard
- Based on WP 34s
- Available on iOS
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WP 31s is a classic RPN scientific calculator based on the powerful but more complex WP 34s. Now available on iOS too (see the support site for other emulators and for the real stuff). It is not programmable but has a rich function set for daily use and is easier to use, thanks to a less cluttered keyboard. A manual can be downloaded at http://sourceforge.net/projects/wp34s/files/doc/Manual_wp_31s_1_2q.pdf/download
Screenshots
Verdict
The clearest difference is price: WP 31s at Free against RPN's $2.99. WP 31s also leads on review sentiment (100% vs 71%) and device support (3 vs 1). RPN's advantage is update cadence (every 4 months vs every 10 months). On rating, ratings volume, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
WP 31s is free to download; RPN costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 4.8 for RPN against 4.9 for WP 31s. Both are backed by a comparable volume of ratings — 6 and 15 respectively. Written reviews are what separate them: 71% of RPN's written reviews are positive against 100% of WP 31s's.
RPN ships an update every 4 months, WP 31s every 10 months. The most recent releases landed on October 23, 2026 and October 24, 2026 respectively.
| Parameter | RPN | WP 31s |
|---|---|---|
| Price | $2.99 | Free — better |
| Rating | 4.8 (6 ratings) | 4.9 (15 ratings) — better |
| Positive reviews | 70.8% of reviews | 100.0% of reviews — better |
| Number of ratings | 6 | 15 — better |
| Update frequency | Every 4 months — better | Every 10 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Free — better |
| Devices | iPad | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 | 12.0 |
| Further details — not scored | ||
| Size | 58 MB | 16 MB |
| Age rating | 4+ | 4+ |
| Developer | CuVee Software | Pascal Meheut |
Customer experience
RPN
WP 31s
In-app purchases
RPN
No in-app purchases
WP 31s
No in-app purchases









