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Plus42

Plus42

Enhanced HP-42S Calc Simulator

79 ratings
39 reviews
🔧 Utilities
$9.99

Details

Released
April 28, 2022
Updated
May 5, 2026

Features

Developer

Thomas Okken
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About

This advanced scientific calculator simulates the classic HP-42S RPN calculator with enhanced features. It offers algebraic expressions, unit conversions, directories for storage, a larger resizable display, financial functions, and 2D plotting with integral and root finding.

✓HP-42S RPN calculator simulation
✓Algebraic expressions
✓Attached units and conversions
✓Program and variable directories
✓Resizable 8-row, 22-column display
✓Time value of money and amortization
✓2D function plotting with zoom and pan
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What's New in Plus42

1.3.15

May 5, 2026

Fixed RLN and RRN for negative numbers in BSIGNED mode.

User reviews

Most RecentHighest RatedLowest Rated

Plus42 fanatic simulator

This is a fantastic HP-42S simulator. Very functional, I use it daily. My HP calculator has long been dead and this allows me to use an RPN scientific calculator in daily engineering tasks. Thank you.
KKAPuser

Not worth of it

Don’t waste your money!
AAAbe Aybar

Best calculator app!

I *LOVE* Free42
Plus42 is even better!
ISIT Problem Solver

Perfection

Once you use an RPN calculator, you will never go back. The HP-42S beats the HP Prime in layout and ease of use for most task, and the enhancements in this implementation is great. I love having the (enhanced) HP-42S always with me on my iPhone whenever I need a calculator.
CSCasually Serious

Can’t convert from DMS to decimal degrees!

WTF. It can easily convert decimal degrees to DMS, but not DMS to decimal degrees?!? What is the point of having one but not the other?!?
Ddhuncth

Response from developer

The function to convert degrees/hours, minutes, and seconds to decimal degrees/hours is called →HR. It's in the CONVERT menu, right next to →HMS. Note that I would have noticed your comment much more quickly if you had emailed me. This space is for app reviews, not for tech support.

See 34 more reviews

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FAQ

What is Plus42?

Plus42 is an advanced scientific programmable calculator that simulates the functionality of the classic HP-42S RPN calculator. It builds upon the Free42 project, offering enhanced features like algebraic expressions, unit conversions, and 2D plotting.

What are the key features of Plus42?

Key features include an HP-42S RPN simulation, algebraic expressions similar to HP-27S, attached units and conversions, directories for organizing programs and variables, a resizable large display, financial functions like TVM and amortization, and 2D plotting with zoom, pan, and root/integral finding.

Is Plus42 free to use?

Yes, Plus42 is a free application. The provided information indicates it does not have in-app purchases or advertisements, suggesting a completely free experience for users.

What kind of calculator is it based on?

It is based on the HP-42S scientific programmable RPN calculator, which was manufactured by Hewlett-Packard from 1988 to 1995. Plus42 is a re-implementation and enhancement of the Free42 project, which itself is a rewrite of the HP-42S.

Who would benefit from using Plus42?

This app is ideal for students, engineers, scientists, and anyone who requires a sophisticated scientific calculator with RPN input. Users who appreciate the legacy of Hewlett-Packard calculators or need advanced features like unit conversions and plotting will find it particularly useful.