Comparison

RPN vs Unit Converter

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

RPN

This app simulates a legendary 1970s programmable calculator, offering advanced features for scientists and engineers. It allows users to run programs, manage virtual cards, and access hundreds of free program cards from its website.

Highlights
  • Virtual program and data cards
  • Virtual paper tape printer
  • Database-driven card manager
  • Create, label, and organize unlimited cards
  • Effortless saving of card collections
  • Formatted program listings
  • Live display of stack and registers
Features
Read full description

A dream calculator of the 70's, priced at $3,200 in today's dollars, now affordable for everyone! RPN-97 Pro is the first complete simulation of Hewlett-Packard's legendary HP-97 programmable calculator for iOS. Produced from 1976 to 1984, the HP-97's features coupled with its capability to store programs on magnetic cards made it a huge success among scientists, engineers and other professionals. Thousands of programs were written for it. Now you can run them right on your iPad, with more ease and faster than ever before. To get you started quickly, download hundreds of program cards from our website for free. What users said: “The most delightful app I possess. The magnet card reader emulation rocks. Would have paid much more for this." "As the owner of an actual working HP 97 calculator, I am blown away with this new simulator. Simply fabulous." "Whoever coded this my hat goes off to you - what a professional piece of work, incredible app." RPN-97 Pro is fully compatible with RPN-67 Pro, its companion simulator of the HP-67 calculator. Features: • Virtual program and data cards • Virtual paper tape printer • Powerful database-driven card manager • Create, label, and organize a virtually unlimited number of cards • Use iTunes to effortlessly save entire card collections on your Mac/PC • Sharing: e-mail, AirDrop, Dropbox, copy, paste, print • Formatted listing clearly showing labels and targets of branches • E-mail listings and let the recipient paste the text right into RPN-97 • Print listings on any AirPrint-compatible printer • Program listing on paper tape shows subroutine nesting • Edit paper tape • E-mail paper tape, or print it via AirPrint • Cut/copy/paste displayed value or program steps • Paste HP-67 or HP-97 listings from other sources into RPN-97 and run them • "Live" display of stack, memory registers, program counter, flags • Show program usage notes • 30 selectable background images, even add your own • Much faster than a real HP-97 • Low-battery indicator (iPad charge 10% or less) • Compatible with RPN-67 Pro and RPN-67 SD, CuVee Software's HP-67 simulators • Supports hardware keyboard While RPN-97 Pro can work exactly like a real HP-97, changing a simple setting will turn the app into a super-charged HP-97: • Up to 999 program steps, 8 subroutine levels, 6 additional flags (F4...F9) • 100 additional registers • 100 additional labels • 100 built-in constants and conversions • More than 150 additional powerful operations and functions Plus: • 15 commands to print and manipulate any range of extended registers • Unrestricted register arithmetic • Exchange x with any register • Complex numbers mode, hyperbolic functions • Non-volatile memory - stack, registers, program, flags, paper tape • Status indicators for prefix keys (EXT, f, LBL, GTO, etc.) • Display showing thousands separators (optional) • Text output on paper tape in 10 colors, even simple plotting • Stack-of-stack: push/pop the entire stack on internal stack (4 levels) • Single-step into subroutines (optional) • Powerful debugging aids, including 10 breakpoints with counters • Keycodes translated to command name while entering or single-stepping a program • Change the duration of the PAUSE command • Cancel SST or BST operation by simply sliding your finger off the depressed key • Compress constants in programs into a single step (reversible) • Use existing programs in text format by a simple paste operation RPN-97 Pro comes with more than 130 programs pre-installed, including HP Standard Pac, HP Business Decisions Pac, HP Math Pac I, HP Stat Pac I, and HP Surveying Pac I. The simulator has been verified to correctly run the examples given in HP Civil Engineering Pac I, HP Clinical Lab Pac, HP E.E. Pac I, HP Games Pac I, HP M.E. Pac I, HP Navigation Pac I, as well as large number of programs published in Users' Library Solutions. For more information and free program downloads visit the RPN-97/67 website: cuveesoft.ch/rpn67

About

Unit Converter

Easily switch between metric and imperial measurements for length, area, mass, temperature, and more. This tool offers quick, accurate conversions with an intuitive interface and offline functionality.

Highlights
  • 15+ unit categories
  • Metric and imperial support
  • Quick and precise conversions
  • Intuitive interface
  • Conversion history
  • Offline functionality
Features
Read full description

Convertly: Your Ultimate Unit Converter Need to convert units quickly and accurately? Convertly makes it easy to switch between measurements with just a few taps. Whether you're converting length, area, mass, temperature, or speed, Convertly has you covered with a wide range of units and an intuitive interface. Key Features: Over 15+ unit categories (Length, Area, Mass, Time, Speed, Temperature & more) Quick and precise conversions Easy-to-use interface Support for both metric and imperial units Conversion history for quick access Works offline – no internet required Download Convertly and make unit conversions faster and easier than ever! Privacy Policy: https://shorturl.at/caL63 Terms of Service: https://shorturl.at/8OwnH

Screenshots

Unit Converter3 screens

Verdict

The call

The clearest difference is price: Unit Converter at Free against RPN's $4.99. RPN's advantage is rating (4.9 vs 1.0) and update cadence (every 3 months vs every 13 months). On ads, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Unit Converter is free to download; RPN costs $4.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

RPN holds the better App Store score, 4.9 against 1.0. That said, the two scores are not equally well evidenced: RPN has 11 ratings behind it against 1, so its average is the more settled of the two.

UpkeepUpdate frequency

RPN ships an update every 3 months, Unit Converter every 13 months. The most recent releases landed on November 1, 2026 and November 4, 2026 respectively.

Scorecard6 real differences · 4 level
RPN versus Unit Converter: the parameters behind the verdict, then further details
ParameterRPNUnit Converter
Price$4.99Free — better
Rating4.9 (11 ratings) — better1.0 (1 ratings)
Positive reviews100.0% of reviews—
Number of ratings11 — better1
Update frequencyEvery 3 months — betterEvery 13 months
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
DevicesiPadiPhone, iPad — better
Requires iOS12.0 — better26.0
Further details — not scored
Size75 MB0 MB
Age rating4+4+
DeveloperCuVee SoftwareMaarten Borsje

Customer experience

RPN

All ratings11 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews12 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Unit Converter

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%

In-app purchases

None

RPN

No in-app purchases

None

Unit Converter

No in-app purchases

Questions

Is RPN free?
RPN costs $4.99, with no in-app purchases.
Is Unit Converter free?
Unit Converter is free to download, with no in-app purchases.
Which has better reviews, RPN or Unit Converter?
RPN is rated higher. RPN averages 4.9 out of 5 from 11 ratings, while Unit Converter averages 1.0 from 1 ratings.
Do RPN or Unit Converter have ads?
Neither RPN nor Unit Converter shows ads.
Which is updated more often, RPN or Unit Converter?
RPN ships an update every 3 months, and Unit Converter every 13 months. Most recently, RPN was updated on November 1, 2026 and Unit Converter on November 4, 2026.

Other comparisons