RPN vs Plus42
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app is a photo-realistic simulation of the classic HP-25 scientific calculator. It offers advanced programming features, a vast function library, and modern enhancements for enhanced usability on iOS devices.
- Photo-realistic simulation
- Programmable (99/999 steps)
- 15 user-defined function keys
- 100 symbolic labels
- 100 visible registers
- Program library with 150+ programs
- Over 270 functions
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RPN-25 CE is a photo-realistic simulation of Hewlett-Packard's highly popular scientific calculator HP-25 for the iPhone. Produced from August 1975 through 1978, it was the "Squash" member of the second-generation HP calculators known as the "Woodstock" series. It was also the first programmable calculator costing less than $200. RPN-25 CE simulates the HP-25C version released in July 1976. Its major improvement in that update was "Continuous Memory". While the simulator works just like the original calculator, a number of carefully designed extensions make it massively more powerful. Features: • Photo-realistic look • Programmable (99 or 999 steps), subroutines, conditional loops, branching • Insert and delete steps with automatic address correction • 15 user-defined function keys of up to 6 characters each, redefinable under program control • Programmable text messages • Program Auto-Start option upon loading • 100 symbolic labels • 100 visible registers, "non-volatile", with unrestricted store/recall arithmetic • 100 flags, visible at a glance • Single-step constants • Program comments • Program library with more than 150 programs pre-installed • More than 270 functions and operations not available on the HP-25 • 100 sounds built-in • Much faster than the original • "Live" register view supporting user interaction (run/stop, single-stepping) • "Live" stack view • Thousands separator (optional) • High-contrast display (optional) • Selectable pause length (up to a day) • Program listing view with program title and description • Program library view • Store, name and retrieve any number of programs • Sharing: Files, iCloud Drive, e-mail, AirDrop, Dropbox, copy, paste, print • Import and run RPN-32 CE and GO-25 programs • Run a large number of HP-41 programs with little or no changes • Clock display (AM/PM or 24h) • Supports Dark Mode Calculator functions: • Statistics, including clearing statistics registers only • Factorial for arbitrary arguments • Trigonometric functions (degrees, radians, grads) • Polar/rectangular conversions • Inverse, square root, logarithm, exponential, Pi • Percentage • Storage arithmetic (store and recall) • Extended stack operations • Low-battery warning • Sound alerts • ..and many, many more Details: cuveesoft.ch/rpn25
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 rating: Plus42 at 4.9 against RPN's 4.3. Plus42 also leads on update cadence (weekly vs every 2 months) and review sentiment (92% vs 80%). RPN's advantage is price ($2.99 vs $9.99) and iOS requirement (12.0 vs 15.0). On ads, in-app purchases and device support 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 $2.99 and Plus42 $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Plus42 holds the better App Store score, 4.9 against 4.3. That said, the two scores are not equally well evidenced: Plus42 has 79 ratings behind it against 10, so its average is the more settled of the two. Written reviews point the same way: 80% of RPN's written reviews are positive against 92% of Plus42's.
RPN ships an update every 2 months, Plus42 weekly. The most recent releases landed on October 24, 2026 and October 27, 2026 respectively.
| Parameter | RPN | Plus42 |
|---|---|---|
| Price | $2.99 — better | $9.99 |
| Rating | 4.3 (10 ratings) | 4.9 (79 ratings) — better |
| Positive reviews | 80.0% of reviews | 92.3% of reviews — better |
| Number of ratings | 10 | 79 — better |
| Update frequency | Every 2 months | Weekly — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Free — better |
| Best chart rank | — | #69 — better |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 — better | 15.0 |
| Further details — not scored | ||
| Size | 28 MB | 11 MB |
| Age rating | 4+ | 4+ |
| Developer | CuVee Software | Thomas Okken |
Customer experience
RPN
Plus42
In-app purchases
RPN
No in-app purchases
Plus42
No in-app purchases









