Comparison

RPN Calc vs Halcyon Calc

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

Head to head
About

RPN Calc

This app provides a straightforward reverse Polish notation (RPN) calculator experience, inspired by classic HP models. It offers a clean interface with large buttons for quick calculations on iPhone, iPad, and Apple Watch, along with a convenient Today Extension for immediate access.

Highlights
  • Reverse Polish Notation (RPN) input
  • Clean, simple interface
  • Large, easy-to-press buttons
  • iPhone, iPad, and Apple Watch support
  • Today Extension for quick access
Features
Read full description

A simple reverse polish notation calculator loosely based on my trusty HP-32SII that runs on iPhone, iPad, and Apple Watch! If you are familiar with HP RPN calculators, the operation of this calculator should seem very straightforward - albeit simplified. It can't be programmed, and it doesn't handle binary, or hexadecimal numbers. But, it has a clean, simple interface with large, easy to press buttons. It has all of the functions required for quick calculations when your iPhone is handier than your computer or calculator. And, remember those cool calculator watches from the 1980s? Unfortunately, none of them were RPN. RPN Calc brings a reverse polish notation watch calculator to the Apple Watch! In addition to the standard RPN Calculator app that runs on iPhone, iPad, and Apple Watch, RPN Calc includes a handy micro RPN Calc Today Extension available for convenient access to quick calculations from the pull down Today screen.

About

Halcyon Calc

A powerful calculator app for students, engineers, and scientists. It handles complex numbers, symbolic expressions, unit conversions, and matrix operations, with advanced plotting and programming capabilities.

Highlights
  • Complex number calculations
  • Symbolic expression manipulation
  • Unit conversion with custom units
  • Matrix and vector operations
  • Symbolic plotting
  • Programming of custom operations
  • Statistical data analysis
Features
Read full description

For students, engineers, scientists or people who fondly remember classic calculators, Halcyon Calc is a great application for manipulating numbers and even symbolic expressions. Features: - Use this calculator on an iPhone, iPod Touch or an iPad - Use your finger to quickly scroll through the stack to review intermediate results - Copy and paste support - Over 225 built-in operations, including trig, logarithms, real functions, complex operations and more - Allows you to work with real, complex and integer numbers. - Real and complex numbers can be displayed in standard, fixed, scientific and engineering format - Use over 120 built-in units to perform unit conversion or create your own units if the one you want is not already there - Integer numbers can be displayed in decimal, hexadecimal, octal and binary bases - Work with real and complex matrices and vectors. - Enter symbolic expressions and solve them for different values. Even better, solve quadratic formulas, collect and expand factors and terms, find minima, maxima and roots of any expression. - Plot symbolic expressions in X/Y coordinates. Pan the coordinate space by dragging the plot in any direction. Zoom in and out using a pinch gesture. - Determine symbolic derivative, taylor series or numeric integral of an expression. - Store numbers, lists, strings and expressions in symbols. Create hierarchies of symbols to allow you to organize your calculations. - Create sequences of calculator commands into programs, creating your own operations which you can then include in expressions. - Store statistical data and calculate totals, averages, standard deviations, linear regressions, etc over that data. - Calculate the probabilities associated with standard distributions like the normal, F and T distributions.

Screenshots

RPN Calc3 screens
Halcyon Calc4 screens

Verdict

The call

The clearest difference is review sentiment: Halcyon Calc at 100% against RPN Calc's 34%. Halcyon Calc also leads on rating (4.9 vs 4.0) and ratings volume (18 vs 6). RPN Calc's advantage is price ($0.99 vs $4.99). On update cadence, 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

RPN Calc costs $0.99 and Halcyon Calc $4.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Halcyon Calc holds the better App Store score, 4.9 against 4.0. Both are backed by a comparable volume of ratings — 6 and 18 respectively. Written reviews point the same way: 34% of RPN Calc's written reviews are positive against 100% of Halcyon Calc's.

UpkeepUpdate frequency

RPN Calc ships an update every 3 months, Halcyon Calc every 4 months. The most recent releases landed on November 8, 2026 and November 6, 2026 respectively.

Scorecard5 real differences · 5 level
RPN Calc versus Halcyon Calc: the parameters behind the verdict, then further details
ParameterRPN CalcHalcyon Calc
Price$0.99 — better$4.99
Rating4.0 (6 ratings)4.9 (18 ratings) — better
Positive reviews34.3% of reviews100.0% of reviews — better
Number of ratings618 — better
Update frequencyEvery 3 months — betterEvery 4 months
AdsNoNo
In-app purchasesNoNo
MonetizationFree — betterPaid
DevicesiPhone, iPad, Apple Watch — betteriPhone, iPad
Requires iOS16.0 — better16.6
Further details — not scored
Size3 MB10 MB
Age rating4+4+
DeveloperJames MattisHalcyon Touch Software

Customer experience

RPN Calc

All ratings6 ratings
Positive83.3%
Neutral0.0%
Negative16.7%
Written reviews35 reviews
Positive34.3%
Neutral14.3%
Negative51.4%

Halcyon Calc

All ratings18 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews13 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

RPN Calc

No in-app purchases

None

Halcyon Calc

No in-app purchases

Questions

Is RPN Calc free?
RPN Calc costs $0.99, with no in-app purchases.
Is Halcyon Calc free?
Halcyon Calc costs $4.99, with no in-app purchases.
Which has better reviews, RPN Calc or Halcyon Calc?
Halcyon Calc is rated higher. RPN Calc averages 4.0 out of 5 from 6 ratings, while Halcyon Calc averages 4.9 from 18 ratings.
Do RPN Calc or Halcyon Calc have ads?
Neither RPN Calc nor Halcyon Calc shows ads.
Which is updated more often, RPN Calc or Halcyon Calc?
RPN Calc ships an update every 3 months, and Halcyon Calc every 4 months. Most recently, RPN Calc was updated on November 8, 2026 and Halcyon Calc on November 6, 2026.

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