RPN User Reviews

Customer Experience

Positive experience81.8% of reviews
Neutral0.0% of reviews
Negative experience18.2% of reviews

~ Based on 11 written reviews from the US App Store.

Is RPN Safe?

Not enough ratings yet to assess RPN.

Is RPN Legit?

RPN-45 SD appears to be a legitimate app. AppsHunter Legitimacy Score for RPN is 80/100.

Based on 80 of 100 points across 7 verification signals from App Store and developer data.

Top reviews

Delay in entering

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.

Sevens look like ones

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

A classic, with a lot of extras

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.
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HP 45

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
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Best by Far

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

Best Classic HP RPN so far...

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.
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Excellent!

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.
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Outstanding

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

A must-have for RPN lovers

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

Very nicely done!

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.
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Schönster Rechner im Store

Aber diese App ist nicht nur mit viel Liebe sehr nah am klassischen Original gestaltet sondern auch für heutige Ansprüche sehr funktional.
Ich würde mir nur wünschen, dass man die iPhone Statuszeile ausblenden kann, diese lenkt mitunter doch beim Blick auf das Display ab und ohne sie wäre der Rechner noch etwas schlanker und somit noch näher am Original.
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