RPN vs DB50X
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 a classic Hewlett-Packard programmable scientific calculator from the 1970s. It includes a 100-hour digital timer, clock functions, and original HP programs.
- Photo-realistic look-and-feel
- Programmable with conditional branching
- 100-hr timer and 12/24-hr clock
- Original HP programs built-in
- Extended features for enhanced usability
- Sharing via email, AirDrop, and more
Read full descriptionHide full description
RPN-55 SD is the first photo-realistic simulation for the iPhone of Hewlett-Packard's low-cost alternative to the famous HP-65 programmable scientific calculator. Produced from 1975 through 1977, it was the "Merlin" member of the classic HP calculator series, priced at $395. HP claimed that it featured "(...) more pre-programmed functions than any other scientific pocket calculator in the world." A main feature of the HP-55 was a crystal-controlled 100-hr digital timer with the ability to store times while the timer was running and later recall them. On RPN-55 SD the timer may also act as a 12-hr or 24-hr clock, including date and weekday display. While the simulator works just like the original calculator – except being much faster and having twice the program memory – you can turn on extended features to make it even more enjoyable to use. RPN-55 SD comes complete with original HP programs built in. Features: • Photo-realistic look-and-feel • Vintage mode or Extended mode • Programmable (99 steps), conditional branching • Insert and delete steps with automatic address correction • Delete range of steps • Subroutines (4 levels) • 20 registers, "continuous", with unrestricted store/recall arithmetic • "Live" register view • Program listing view • Program library view • Store and retrieve any number of programs • 100-hr timer supporting 10 split times and 12/24-hr clock mode with date • Swap unit conversions with additional functions, e.g. hyperbolics • Sharing: e-mail, AirDrop, Dropbox, copy, paste, print • 112 programs pre-installed Calculator functions: • Statistics (linear regression, mean, standard deviation, correlation coefficient, x- and y-estimates) • Trigonometric functions (degrees, radians, grads) • Polar/rectangular conversions • Inverse, square root, logarithm, exponential, pi • Storage arithmetic (store and recall) • Percent, absolute, integer, fractional value, round • Factorial • Random number • Unit and hours conversions Details: cuveesoft.ch/rpn55
DB50X
This scientific calculator offers high-precision computations with arbitrary precision for numbers. It supports advanced functions like complex numbers, matrices, symbolic calculations, and graphing, with a user-friendly interface and extensive built-in help.
- Arbitrary precision calculations
- RPN and algebraic operations
- Complex numbers, vectors, matrices
- Symbolic and numerical solving
- Graphing and plotting
- Engineering units and constants
- Unicode text support
Read full descriptionHide full description
DB50X is a new high-precision scientific calculator inspired by the legendary HP50G series from Hewlett-Packard. It is not an emulator, but a redesign from scratch, which is faster, and delivers never seen before capabilities like computations in arbitrary precision. Like the original HP50G, DB48X supports an unlimited stack, RPN and algebraic operations, complex numbers, based numbers, vectors, matrices, text, symbolic computations, numerical solving and integration, graphing and plotting, statistics, engineering units, and well over 1000 built-in functions. It integrates a library of equations and constants covering mathematics, physics or chemistry. Using modern technologies, DB50X goes well beyond the original HP50G in many ways: - It is significantly faster, uses less memory, and features a higher-resolution 240x400 pixels graphical color display. - Integer and decimal values can have an arbitrarily large number of digits, so you can compute log(pi) with 200 digits in a few keystrokes. - The six function keys feature up to three function per key, giving quick access to up to 18 related functions at a time. - Complex numbers can mix and match polar and rectangular form. - Symbolic operations extend to complex numbers, vectors and matrices. - Based numbers can be in any base from 2 to 36, and support any number of bits, making it easy to emulate a 23-bit or 512-bit processor. - Text is represented using Unicode instead of the proprietary HP encoding, facilitating data exchange with the rest of the world. - Multiple graphs can be distinguished using colour patterns - Engineering units include all the modern evolutions of the SI system, and can be configured by the user, e.g. to integrate currency units with the exchange rate du jour. Converting between USD/hour and EUR/day has never been so easy! - A built-in hyperlinked help system documents functions simply by holding the corresponding key, and combine a quick start guide, a user manual and a reference manual. - Over 700K of memory is available for RPL programs. - Access to iCloud to save your program and edit them from your Mac. DB508X will run many user RPL programs designed for the HP48, HP49 or HP50 directly as is. However, since it is not an emulator, it will not run any HP binary object, and notably will not run HP50G games or anything involving system RPL. This is an early-access release. Please consult https://github.com/c3d/db48x/blob/stable/doc/5-Unimplemented.md for a list of commands that are not yet implemented. DB50X is part of a family of related calculators that include the black-and-white DB48X and the entry-level DB40X.
Screenshots
Verdict
The clearest difference is price: RPN at $1.99 against DB50X's $9.99. RPN also leads on iOS requirement (12.0 vs 14.0). DB50X's advantage is update cadence (every 3 weeks vs every 3 months). On rating, review sentiment, ratings volume and ads 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 $1.99 and DB50X $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 — 5.0 for RPN against 5.0 for DB50X. Both are backed by a comparable volume of ratings — 8 and 8 respectively. Written reviews split almost evenly too, at 100% and 100% positive.
RPN ships an update every 3 months, DB50X every 3 weeks. The most recent releases landed on September 6, 2026 and September 24, 2026 respectively.
| Parameter | RPN | DB50X |
|---|---|---|
| Price | $1.99 — better | $9.99 |
| Rating | 5.0 (8 ratings) | 5.0 (8 ratings) |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| Number of ratings | 8 | 8 |
| Update frequency | Every 3 months | Every 3 weeks — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 — better | 14.0 |
| Further details — not scored | ||
| Size | 17 MB | 7 MB |
| Age rating | 4+ | 4+ |
| Developer | CuVee Software | Christophe de Dinechin |
Customer experience
RPN
DB50X
In-app purchases
RPN
No in-app purchases
DB50X
No in-app purchases








