RPN vs Plus42
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app simulates a legendary 1970s programmable calculator, offering advanced features for scientists and engineers. It allows users to run programs, manage virtual cards, and access hundreds of free program cards from its website.
- Virtual program and data cards
- Virtual paper tape printer
- Database-driven card manager
- Create, label, and organize unlimited cards
- Effortless saving of card collections
- Formatted program listings
- Live display of stack and registers
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A dream calculator of the 70's, priced at $3,200 in today's dollars, now affordable for everyone! RPN-97 Pro is the first complete simulation of Hewlett-Packard's legendary HP-97 programmable calculator for iOS. Produced from 1976 to 1984, the HP-97's features coupled with its capability to store programs on magnetic cards made it a huge success among scientists, engineers and other professionals. Thousands of programs were written for it. Now you can run them right on your iPad, with more ease and faster than ever before. To get you started quickly, download hundreds of program cards from our website for free. What users said: “The most delightful app I possess. The magnet card reader emulation rocks. Would have paid much more for this." "As the owner of an actual working HP 97 calculator, I am blown away with this new simulator. Simply fabulous." "Whoever coded this my hat goes off to you - what a professional piece of work, incredible app." RPN-97 Pro is fully compatible with RPN-67 Pro, its companion simulator of the HP-67 calculator. Features: • Virtual program and data cards • Virtual paper tape printer • Powerful database-driven card manager • Create, label, and organize a virtually unlimited number of cards • Use iTunes to effortlessly save entire card collections on your Mac/PC • Sharing: e-mail, AirDrop, Dropbox, copy, paste, print • Formatted listing clearly showing labels and targets of branches • E-mail listings and let the recipient paste the text right into RPN-97 • Print listings on any AirPrint-compatible printer • Program listing on paper tape shows subroutine nesting • Edit paper tape • E-mail paper tape, or print it via AirPrint • Cut/copy/paste displayed value or program steps • Paste HP-67 or HP-97 listings from other sources into RPN-97 and run them • "Live" display of stack, memory registers, program counter, flags • Show program usage notes • 30 selectable background images, even add your own • Much faster than a real HP-97 • Low-battery indicator (iPad charge 10% or less) • Compatible with RPN-67 Pro and RPN-67 SD, CuVee Software's HP-67 simulators • Supports hardware keyboard While RPN-97 Pro can work exactly like a real HP-97, changing a simple setting will turn the app into a super-charged HP-97: • Up to 999 program steps, 8 subroutine levels, 6 additional flags (F4...F9) • 100 additional registers • 100 additional labels • 100 built-in constants and conversions • More than 150 additional powerful operations and functions Plus: • 15 commands to print and manipulate any range of extended registers • Unrestricted register arithmetic • Exchange x with any register • Complex numbers mode, hyperbolic functions • Non-volatile memory - stack, registers, program, flags, paper tape • Status indicators for prefix keys (EXT, f, LBL, GTO, etc.) • Display showing thousands separators (optional) • Text output on paper tape in 10 colors, even simple plotting • Stack-of-stack: push/pop the entire stack on internal stack (4 levels) • Single-step into subroutines (optional) • Powerful debugging aids, including 10 breakpoints with counters • Keycodes translated to command name while entering or single-stepping a program • Change the duration of the PAUSE command • Cancel SST or BST operation by simply sliding your finger off the depressed key • Compress constants in programs into a single step (reversible) • Use existing programs in text format by a simple paste operation RPN-97 Pro comes with more than 130 programs pre-installed, including HP Standard Pac, HP Business Decisions Pac, HP Math Pac I, HP Stat Pac I, and HP Surveying Pac I. The simulator has been verified to correctly run the examples given in HP Civil Engineering Pac I, HP Clinical Lab Pac, HP E.E. Pac I, HP Games Pac I, HP M.E. Pac I, HP Navigation Pac I, as well as large number of programs published in Users' Library Solutions. For more information and free program downloads visit the RPN-97/67 website: cuveesoft.ch/rpn67
Plus42
This advanced scientific calculator simulates the classic HP-42S RPN calculator with enhanced features. It offers algebraic expressions, unit conversions, directories for storage, a larger resizable display, financial functions, and 2D plotting with integral and root finding.
- HP-42S RPN calculator simulation
- Algebraic expressions
- Attached units and conversions
- Program and variable directories
- Resizable 8-row, 22-column display
- Time value of money and amortization
- 2D function plotting with zoom and pan
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Plus42 is an advanced scientific programmable calculator, based on Free42. Free42, in turn, is a complete re-implementation of the HP-42S scientific programmable RPN calculator, which was made from 1988 until 1995 by Hewlett-Packard. Free42 is a complete rewrite and contains no HP code whatsoever. Plus42 builds on Free42 and adds: Algebraic expressions modeled after those used on the HP-27S and HP-17B/19B; attached units and unit conversions modeled after those used on the HP-48/49/50 series; directories for more organized storage of programs and variables; a larger display, with 8 rows and 22 columns (131x64 pixels) by default, which the user may resize at will; time value of money and amortization schedules; and two-dimensional plotting of functions, with ability to zoom and pan, and find integrals and roots from points in the plot.
Screenshots
Verdict
The clearest difference is update cadence: Plus42 at weekly against RPN's every 3 months. Plus42 also leads on chart position (#195 vs unranked) and ratings volume (79 vs 11). RPN's advantage is price ($4.99 vs $9.99). On rating, review sentiment, 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
RPN costs $4.99 and Plus42 $9.99 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 — 4.9 for RPN against 4.9 for Plus42. That said, the two scores are not equally well evidenced: Plus42 has 79 ratings behind it against 11, so its average is the more settled of the two. Written reviews are what separate them: 100% of RPN's written reviews are positive against 92% of Plus42's.
RPN ships an update every 3 months, Plus42 weekly. The most recent releases landed on June 1, 2026 and September 22, 2026 respectively.
| Parameter | RPN | Plus42 |
|---|---|---|
| Price | $4.99 — better | $9.99 |
| Rating | 4.9 (11 ratings) — better | 4.9 (79 ratings) |
| Positive reviews | 100.0% of reviews — better | 92.3% of reviews |
| Number of ratings | 11 | 79 — better |
| Update frequency | Every 3 months | Weekly — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Free — better |
| Best chart rank | — | #195 — better |
| Devices | iPad | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 | 12.0 |
| Further details — not scored | ||
| Size | 75 MB | 11 MB |
| Age rating | 4+ | 4+ |
| Developer | Willy Kunz | Thomas Okken |
Customer experience
RPN
Plus42
In-app purchases
RPN
No in-app purchases
Plus42
No in-app purchases









