# RPN-45 SD — Vintage Calculator (1973)

> A photorealistic simulation of the 1973 HP-45 scientific calculator with modern enhancements. (iPhone/iPad app by CuVee Software.)

- Source: https://appshunter.io/ios/app/rpn-45-sd/id509923051 (this page in markdown: same URL + `.md`)
- Developer: [CuVee Software](https://appshunter.io/developer/424873503)
- Category: Productivity, Utilities
- Price: $1.99
- Rating: 4.30/5 from 15 App Store ratings · 11 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.0 · 14 MB
- Languages: American English, German (Germany), European Spanish
- Released: 2012-03-17
- Data updated: 2026-08-26
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/rpn-45-sd/id509923051/reviews.md

## What is RPN?

RPN-45 SD is a complete simulation of the scientific hand-held calculator HP-45 from 1973. Powerful enhancements turn the calculator into an amazingly useful tool for the 21st century.

Features:

• Photo-realistic look based on an existing device
• Original LED display or high-contrast LCD display
• Printer to keep a record of calculations
• Animated keys with adjustable click sound and visual feedback
• Simulation of the HP-45's computation times (may be disabled)
• All functions and operations of the HP-45 fully implemented
• "Secret" stopwatch implemented, extensible from 12 to 100 hours capacity
• Stopwatch may be preset to current time
• Swipe left across display to correct wrong number entries
• Cut/copy/paste of display value
• Tap display to show stack and all memory registers
• Complex numbers may be used in almost all operations
• Non-volatile stack and registers
• 18 storage locations (9 in complex number mode)
• Exponentiation and factorial accept any values (incl. complex)
• Optional hyperbolic functions
• Logarithm to any base (incl. complex)
• Solve linear equations in two or three unknowns
• Solve quadratic and cubic equations
• Normal distribution, Pearson correlation coefficient of paired variables
• Linear regression with estimates
• Weighted mean
• Permutation, Combination (binomial coefficient)
• Integer and fractional part of a number
• Display rounding
• Random numbers in any range, integer or real
• Day of the week of any date between Jan 1, 0001 and Dec 31, 9999
• Easter date for any year between 1583 and 4099
• Support for Julian dates
• Date and day of the week a number of days away (past or future)
• Number of days between any two dates
• Last Stack operation
• Show display value in hexadecimal
• Percentage of sum
• Register arithmetic includes summation registers and LAST x
• Indicators for active prefix keys
• Angular mode indicator
• Localized decimal point
• Thousand's separator
• Clear all registers
• Backup registers in a protected area

Double-tap the display for some basic hints.

Also available for iPad (RPN-45 HD).

For more information, a manual and sample calculations visit the RPN-45 website: cuveesoft.ch/rpn45/en


What users said:

"Have been using HP RPN calculators since HP-35 first came out. The CuVée versions for Apple products are the best emulations by far. I have, and regularly use, them all."

"This app is a great emulator of the classic HP-45 Scientific Calculator, in look, feel and function. It keeps getting better and better with each update."

"This is the most like the real thing that I've used. I've bought others but keep coming back to this App. It's photorealistic, the LEDs appear the way the real ones do, and the buttons almost give the same satisfying feedback of the real thing."

## Key features

- Photorealistic calculator simulation
- Full HP-45 function implementation
- Complex number support
- Advanced date and time functions
- Printer simulation for calculation records
- Stopwatch functionality
- Cut/copy/paste display values

## Recent user reviews (10 of 11)

All indexed reviews: https://appshunter.io/ios/app/rpn-45-sd/id509923051/reviews.md

### 2/5 — Delay in entering

*2025-11-18*

I’ve had this app for many years, and has been a 5 star app for most of them. Somewhat recently there has been a delay in entering key strokes making it annoying to use. The HD (iPad) version doesn’t seem to suffer the same delay. Unfortunately, the iPhone is where I use it the most.

### 1/5 — Sevens look like ones

*2025-05-01*

The dynamic island of an iPhone 16 covers up the top of the display making the sevens look like ones.

### 4/5 — A classic, with a lot of extras

*2018-04-28*

Fun to have a replica of this machine that I first learned on 45 years ago.

Kind of fun to have the enhancements too, although these do stop short of current high-end apps.  The best part, just as a way for any such app to extend the functionality of the keyboard, is actually the double-mode shift key, which gets you yellow functions on the first push and then red functions on the second push, before cycling back to neutral.  Shows you how little you depend on having the shift key toggle back to neutral on the very next push: pretty rarely. One more push won’t hurt you.

ENGineering display mode is something I use a lot, a nice update to have, and also the HYPerbolics button. And the additional STO/RCL registers are welcome.  And the regression and estimate keys, and permutations/combinations, could come in handy, though I haven’t tried them yet,  And the quadratic/cubic solver.

The complex numbers are a nice addition too, similar to the 15c treatment although with some different special-function keys.

The simultaneous equation solvers are ok too, I suppose, though as matrix math they’re kind of a one-trick pony compared to the 15c’s treatment (Vicinno for instance) which will handle five matrices of any shape, not just three that are one square and two column vectors — and will let you perform any operation you like with them, not just solve simultaneous equations.

So except for the nostalgia trip, my first choice for a capable two-shift-button machine with quickly accessible functions is actually the 15c.  (Which also is programmable.)

Or if you really want a workhorse-machine app you should get Thomas Okken’s Free42 — an open-source rewrite of the HP42s — which has a lot more functions and shows two stack levels and both halves of a complex number, so it’s way easier to keep track of what you’re doing,  And lets you write alphanumeric labels for programs, variables, matrices, etc.  But does pay for having so much power by having many of the functions somewhat buried in menus, not as quick to reach as on the 45 or the 15c,

But I do enjoy having the 45 around, and it does do way more than you’d ever expect a 45 replica to do.

### 5/5 — HP 45

*2016-09-04*

sehr gute App, habe noch meinen Original HP 45 von 1974, hat damals ca 1.500,- DM gekostet, wollte mir immer neuen Akku kaufen, brauche ich Dank dieser App nicht mehr.
Tasten sind etwas gewöhnungsbedürtig, das ist natürlich bei dem größeren Original besser.
Mich stört, das der Tastaturklick immer wieder auf die voreingestellte, viel zu laute, Lautstärke zurückspringt

### 5/5 — Best by Far

*2015-09-06*

Have been using HP RPN calculators since HP-35 first came out. The cuvée versions for Apple products are the best emulations by far. I have, and regularly use, them all.  Keep up the great work

### 5/5 — Best Classic HP RPN so far...

*2014-11-12*

As of 11/12/14 this is the most like the real thing that I've used.  I've bought others but keep coming back to this App.  It's photorealistic, the LEDs appear the way the real ones do, and the buttons almost give the same satisfying feedback of the real thing.  I recently spent 14.99 for ClassicHPCalc for it's HP 35 option.  I was so disappointed that it is not even close to this Apps realism.  I really hope that this developer does an HP 35 version of this at this quality level. I'm proof that there is at least one person here that'll drop $15 bucks for it.

### 5/5 — Excellent!

*2014-10-23*

I've been using a real HP-45 since 1973. Willy Kunz has done an excellent job recreating and then extending the versatility of the real thing in this simulation. I love it! My only gripe is that the gold and pink fonts he used for the extended functions aren't as readable on an iPhone 6 as the gold font he used for the standard functions. Very minor, and easily correctable.

### 5/5 — Outstanding

*2014-08-05*

I got their app for the ipad. This is equally well designed and crafted

### 5/5 — A must-have for RPN lovers

*2014-06-06*

Excellent! New updated FIX function is a big help. Works a lot like my old HP-34c. Highly recommended.

### 5/5 — Very nicely done!

*2013-01-28*

Very nicely done HP-45 emulator, plus the "extra" features are a nice bonus.  Beautifully executed, including the timer mode. I have other calculator emulators with simulated 7 segment LED displays, but none that capture the look of a real vintage 70's display nearly as well as this one. One minor criticism: the shifted key labels are a bit hard to read on an iPod (standard display). Overall an excellent addition to my HP calculator "virtual" collection, and compared to what I've paid for some of them, this one is a real bargain.

## Frequently asked questions about RPN

### What is RPN-45 SD?

RPN-45 SD is a complete simulation of the HP-45 scientific calculator from 1973. It aims to replicate the look, feel, and functionality of the original device while adding modern conveniences.

### What devices does RPN-45 SD support?

RPN-45 SD is available for iPhone and iPod touch. A separate version, RPN-45 HD, is available for iPad.

### How much does RPN-45 SD cost?

RPN-45 SD is a paid application priced at $1.99. There are no in-app purchases or subscriptions.

### Does RPN-45 SD have ads?

No, RPN-45 SD does not contain advertisements. It is a premium application that offers an ad-free experience.

### How often is RPN-45 SD updated?

RPN-45 SD was last updated on March 11, 2026, indicating a history of regular updates to improve functionality and compatibility.

### What are the key features of RPN-45 SD?

Key features include a photorealistic design, full HP-45 function implementation, support for complex numbers, a built-in printer simulation, and advanced date calculation capabilities.

### Is RPN-45 SD suitable for all ages?

RPN-45 SD has an age rating of 4+, making it suitable for a wide range of users. Its complex mathematical functions may be more relevant to older users.

### Can I export my calculations from RPN-45 SD?

Yes, RPN-45 SD features a printer simulation that allows you to keep a record of your calculations, effectively enabling an export of your work.

## Version history (last 5 releases)

### 6.6 — 2026-03-11

Improved compatibility with real HP-45 when using D.MS conversions:

– With "High-speed Calculations" set to off: same results as real HP-45
– With "High-speed Calculations" set to on: improved results (no digits dropped by conversion)


EXAMPLE

Convert 12.345612:

– "High-speed Calculations" off: D.MS-> 12.58225556, then ->D.MS back to 12.34560000
– "High-speed Calculations" on:  D.MS-> 12.58225556, then ->D.MS back to 12.34561200

### 6.5 — 2025-10-16

• Improved compatibility with iPhone Air and iOS 26.

### 6.4 — 2025-07-28

Updated "About" screen shows more options. Double-tap the display to open it.

### 6.3 — 2025-05-10

• Faster startup – no delay until the first button press is recognized after switching on.

### 6.2 — 2025-03-03

• A result like 9.99×10⁹⁹ is now rounded correctly for all decimal point settings, e.g. SCI 1 (in contrast to the original HP-45).

• Certain calculations, e.g. 100⁷⁵, caused the app to crash.

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## More apps by CuVee Software

- [RPN-45 HD](https://appshunter.io/ios/app/rpn-45-hd/id424873500)
- [RPN-70 HD](https://appshunter.io/ios/app/rpn-70-hd/id436127144)
- [Smart Sudoku](https://appshunter.io/ios/app/smart-sudoku/id457564906)
- [Vintage-45](https://appshunter.io/ios/app/vintage-45/id506402272)
- [RPN-67 NP](https://appshunter.io/ios/app/rpn-67-np/id603100249)

All apps by CuVee Software: https://appshunter.io/developer/424873503

## Related topics

[cuvee software](https://appshunter.io/ios/topics/cuvee-software)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-26.*