Comparison

RPN vs Plus42

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

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.

Highlights
  • 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
Features
Read full description

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

About

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.

Highlights
  • 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
Features
Currently charting
Read full description

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

RPN4 screens
Plus424 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

RPN costs $2.99 and Plus42 $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

RPN ships an update every 2 months, Plus42 weekly. The most recent releases landed on October 24, 2026 and October 27, 2026 respectively.

Scorecard8 real differences · 3 level
RPN versus Plus42: the parameters behind the verdict, then further details
ParameterRPNPlus42
Price$2.99 — better$9.99
Rating4.3 (10 ratings)4.9 (79 ratings) — better
Positive reviews80.0% of reviews92.3% of reviews — better
Number of ratings1079 — better
Update frequencyEvery 2 monthsWeekly — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
Best chart rank—#69 — better
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS12.0 — better15.0
Further details — not scored
Size28 MB11 MB
Age rating4+4+
DeveloperCuVee SoftwareThomas Okken

Customer experience

RPN

All ratings9 ratings
Positive88.9%
Neutral0.0%
Negative11.1%
Written reviews5 reviews
Positive80.0%
Neutral0.0%
Negative20.0%

Plus42

All ratings79 ratings
Positive97.5%
Neutral0.0%
Negative2.5%
Written reviews39 reviews
Positive92.3%
Neutral2.6%
Negative5.1%

In-app purchases

None

RPN

No in-app purchases

None

Plus42

No in-app purchases

Questions

Is RPN free?
RPN costs $2.99, with no in-app purchases.
Is Plus42 free?
Plus42 costs $9.99, with no in-app purchases.
Which has better reviews, RPN or Plus42?
Plus42 is rated higher. RPN averages 4.3 out of 5 from 10 ratings, while Plus42 averages 4.9 from 79 ratings.
Do RPN or Plus42 have ads?
Neither RPN nor Plus42 shows ads.
Which is updated more often, RPN or Plus42?
RPN ships an update every 2 months, and Plus42 weekly. Most recently, RPN was updated on October 24, 2026 and Plus42 on October 27, 2026.

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