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.
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User Rating
4.91 out of 5
58 ratings
in United States
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Ratings History
Reviews
Love This
In college I was an HP41C user. Once in my first engineering job I switched to the HP42S which has served me well over my 30+ year career. Once iPhones became a thing, I loaded Thomas’s Free42 and have been using that for a couple decades. I still have a real 42S on my desk for daily use. I recently purchased an HP Prime which is a lovely calculator but it’s just not completely comfortable to use. Switching to Thomas’s Plus42 feels really comfortable and adds lots of lovely features. I will likely purchase a SwissMicro DM42 to be used as my daily desk calc so that my phone app and physical desk calc are similar. That would send the 42S to the vintage calc cabinet. Honestly having this on my phone is massively so functional it’s hard to justify even owning a physical calc but there are times at the desk when it’s nice to grab the physical unit with tactile keys that can’t be interrupted with alerts :-). This is a beautiful upgrade to the free42. Thanks Thomas!
Need multitasking
When using on iPad, the app occupies the whole screen. Currently it does not support multitasking. But it would great to share the screen with other apps (side or floating window).
Beautiful and functional at the same time
Thomas has done an outstanding job on this app! It is not only the most beautiful calculator app out there, but it’s also the most powerful and functional of any of the HP inspired calculator app. The graphics are outstanding and the “extras” that were added in addition to the 42s standard makes the app even more appealing.
If you know how to use a RPN calculator, this IS the one to have and use. If you don’t know how to use a RPN calculator, learn how and buy this.
I always carry my phone, but rarely my physical DM42 or “real” 42s.
You won’t regret getting this app.
Congratulations Thomas for all the work you have done over the years relating to the 42. You should be proud.
The best calculator-computer period
With some programming, this can replace both of my units conversion and finance calculators apps. It is that powerful. I hope - and still have not figured out - we could use and call the TVM variables (PMT, FV, etc) in our custom programs, rather than duplicate the already available functions.
Solid well implemented RPN calculator
This calculator is the one I use first. It's powerfull, excellently done and works allways as expected. Also, it's well maintained. I wish all apps were made with this quality level.
Best Programmable Calculator
Have been using Free42 for years but Plus42 is Free42 on steroids. The new features like Dir and Eqn are great enhancements. Many thanks for to this developer for all his efforts.
Thanks for this app
I have been using free42 for long time and I am glad you are offering a premium version and I can contribute to the developer of a great app.
Amazing reinvented.
I own multiple copies of the HP 42S, the DM42, but unlike those machines, my iPhone is always in my pocket. I have completely uninstalled the default calculator app and use the Free42 application quite heavily. I was really glad to see an upgrade with a bigger screen, so that I have something that’s close to the DM42 in my pocket at all times. This, I tell my students, is the best calculator ever made by man or beast. Thanks, Thomas!
Great RPN calculator!
The only thing an actual HP42 does better than this is the hardware buttons.
If you don’t know what an RPN calculator is, take a few minutes to grasp the concept, give Free42 a try, and math may become a whole lot easier.
Just when we thought Free42 couldn’t get any better this shows up. Well done, convenient, beautiful implementation, solid functionality. I use it every day.
Thank you so much for these apps Thomas!
Lives in my Home Screen
This app goes above and beyond expectations. Very impressive work done to make this calculator what it is. Yes, it’s a bit nostalgic in terms of the looks, but this calculator is super useful! Lots of great loving care went into making this the best modern “HP RPN” calculator on the planet that’s not made by HP, but made by a developer who clearly puts forth passion in his work.
