Comparison

RPN vs Constructive Calculator

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

Constructive Calculator

This calculator performs calculations with arbitrary precision, avoiding rounding errors common in standard calculators. It provides an extensive scientific keypad and can display an unlimited number of digits for exact results.

Highlights
  • Arbitrary-precision calculations
  • Unlimited digit display
  • Scientific keypad
  • Exact results for large numbers
  • Running tape of calculations
  • Locale-aware digit grouping
Features
Read full description

Ordinary calculators round. Constructive Calculator doesn't. It computes with constructive real numbers, an arbitrary-precision engine that keeps every result exact and hands you as many correct digits as you ask for. The rounding errors that quietly accumulate in ordinary calculators simply never happen. AS MANY DIGITS AS YOU WANT A pocket calculator stops at about 15 digits and rounds off the rest. Constructive Calculator keeps every result exact, so the digits a normal calculator throws away are still there. Swipe √2, π, or any answer to pull in tens, hundreds, or thousands more, computed on demand. SCIENTIFIC KEYPAD Trigonometry in degrees or radians and their inverses, exponentials and logarithms, powers and roots, factorials, percentages, the constants π and e, and the standard normal distribution, its CDF Φ and quantile Φ⁻¹, computed to the same arbitrary precision as everything else. BIG INTEGERS, IN FULL 52! (the number of ways to shuffle a deck) prints in full, all 68 of its digits, with no scientific-notation hand-waving. BUILT FOR CLARITY A running tape of recent calculations, locale-aware digit grouping, and copy at whatever precision you need. Constructive Calculator is an independent port of Hans Boehm's constructive-reals calculator, rebuilt natively for iPhone and iPad.

Screenshots

Constructive Calculator4 screens

Verdict

The call

The clearest difference is price: Constructive Calculator at Free against RPN's $4.99. Constructive Calculator also leads on update cadence (every 8 days vs every 3 months). RPN's advantage is ratings volume (11 vs 1) and iOS requirement (12.0 vs 16.0). On rating, 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

Constructive Calculator 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

On the App Store both sit at effectively the same score — 4.9 for RPN against 5.0 for Constructive Calculator. 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, Constructive Calculator every 8 days. The most recent releases landed on October 20, 2026 and October 28, 2026 respectively.

Scorecard5 real differences · 5 level
RPN versus Constructive Calculator: the parameters behind the verdict, then further details
ParameterRPNConstructive Calculator
Price$4.99Free — better
Rating4.9 (11 ratings)5.0 (1 ratings) — better
Positive reviews100.0% of reviews—
Number of ratings11 — better1
Update frequencyEvery 3 monthsEvery 8 days — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
DevicesiPadiPhone
Requires iOS12.0 — better16.0
Further details — not scored
Size75 MB1 MB
Age rating4+4+
DeveloperCuVee SoftwareDmitriy Mayorov

In-app purchases

None

RPN

No in-app purchases

None

Constructive Calculator

No in-app purchases

Questions

Is RPN free?
RPN costs $4.99, with no in-app purchases.
Is Constructive Calculator free?
Constructive Calculator is free to download, with no in-app purchases.
Which has better reviews, RPN or Constructive Calculator?
Constructive Calculator is rated higher. RPN averages 4.9 out of 5 from 11 ratings, while Constructive Calculator averages 5.0 from 1 ratings.
Do RPN or Constructive Calculator have ads?
Neither RPN nor Constructive Calculator shows ads.
Which is updated more often, RPN or Constructive Calculator?
RPN ships an update every 3 months, and Constructive Calculator every 8 days. Most recently, RPN was updated on October 20, 2026 and Constructive Calculator on October 28, 2026.

Other comparisons