Plus42 4+

Thomas Okken

    • 5.0 • 29 Ratings
    • $9.99

iPhone Screenshots


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.

What’s New

Version 1.0.11

Fixed crash in SHOW for certain complex numbers.

Added A...F function. This allows programs to turn on HEXM mode with the A...F menu activated.

Added UBASE and UVAL to the equation parser.

PLOT: Fixed coordinate rounding at the top of the display.

Raised precedence of _ operator, so expressions like 40000_"km"/1_"d" can now be written without parentheses.

The direct solver now converts the solution to match the units of the previous value of the variable being solved for, if it existed already and had compatible units. In all other cases, the variable is overwritten, as before.

Added Calculator / Print-Out swipe direction configuration option to Preferences.

Fixed incorrect Out of Range error returned by BASE functions in certain cases, e.g. BRESET 64 WSIZE 1 ENTER BASE÷

Ratings and Reviews

5.0 out of 5
29 Ratings

29 Ratings

akhan.a ,

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!

DarkRadon ,

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.

LE2357 ,

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.

App Privacy

The developer, Thomas Okken, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    Up to six family members can use this app with Family Sharing enabled.

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