Comparison

Calca vs RPN

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

Head to head
About

Calca

This app is an advanced symbolic calculator and text editor. It solves equations, simplifies expressions, and allows you to explain your work alongside calculations. Calculations update instantly as you type, and all data is stored as plain text for easy sharing and device syncing.

Highlights
  • Symbolic calculation
  • Equation solving
  • Expression simplification
  • Markdown text editor
  • Real-time updates
  • Unit and currency conversion
  • Matrix operations
Features
Read full description

Calca is a powerful symbolic calculator that gives you instant answers as you type. It solves equations and simplifies complex expressions - it's a computer algebra system in your pocket! It's also a rich Markdown text editor so that you can explain your ideas alongside your calculations. Calca is perfect for professionals and students - anyone who works with numbers and equations. Variables and functions can be created with only a few keystrokes and can be manipulated with a rich library of operators and functions. Calca updates as you type - just like a spreadsheet. You can declare variables, edit their values and watch everything update before your eyes. Since everything is calculated on the device - no network needed - you get answers instantaneously. All calculations are stored as plain text so you can easily share them with other editors and move them from device to device. Calca has been designed to work with iCloud documents so all your devices can access your calculations - you'll always have the latest files ready for viewing and editing. Calca comes with a suite of examples to help you get started covering topics from home mortgages to kinetics. All these examples are fully explained within Calca itself. Are you still using a desktop calculator? Are you using the calculator with the giant buttons that came with your OS? Computers are much more capable than doing simple one-line arithmetic - put your machine to work with Calca! Calculation Features: • Variables `x = 42` • Functions `f(c) = 9/5*c + 32` and even recursive functions • Units `42 mph in kmph` and currency `¥599 in $` • Solves equations (`x + 2x + 4x = 42`, what is x?) • Matrices with inverses so you can solve linear equations • Sum, prod, map, and reduce operations on lists, matrices, and ranges • Trigonometry and complex numbers • Derivatives of functions • Logic operations and if statements • Binary math (& and |) and support for binary and hex number (`0xA9` and `0b1010`) • Keeps track of units (m, s, m/s, m/s^2, etc.) so you can verify your equations as you compute Please visit http://calca.io to see lots of examples. Thank you for looking!

About

RPN

This app is a photo-realistic simulation of a classic Hewlett-Packard programmable business calculator. It offers advanced programming features, extensive register memory, and a library of pre-installed programs for various financial and statistical calculations.

Highlights
  • Photo-realistic look-and-feel
  • Programmable with subroutines and flags
  • 20 registers with unlimited store/recall
  • Indirect register addressing
  • Program library and sharing
  • Financial and statistical functions
  • Date and calendar calculations
Features
Read full description

RPN-38 CX is the first photo-realistic simulation of Hewlett-Packard's popular high-end programmable business calculator HP-38C for the iPhone. Produced from 1979 through 1983, it was the "Chive" member of the third-generation HP calculators known as the "Spice" series. While the simulator works like the original calculator, a number of carefully designed extensions make it a lot easier to use. RPN-38 CX is fully compatible with the HP-12C, except for calculations and programs involving Bonds and Depreciation. Features: • Photo-realistic look-and-feel • Programmable (99 steps, program memory not shared with register memory) • Subroutines, flags, loop control, extended conditional branching • Insert and delete steps with automatic address correction • 20 registers, "continuous", with unlimited store/recall arithmetic • Indirect register addressing • Register view • Program listing view • Program library view • Additional functions (nominal and effective interest rate) • Shortcuts for often-used key combinations • Store and retrieve any number of programs • Sharing: e-mail, AirDrop, Dropbox, copy, paste, print • 40 programs pre-installed Calculator functions: • Percentage (%, ∆%, %Total) • Simple and Compound Interest • Optional odd periods (like HP-12) • Nominal/Effective interest rate conversion • Amortization • Discounted Cash Flow Analysis • Net Present Value, Internal Rate of Return • Date and Calendar (actual or 30/360 day basis) • Statistics (mean, weighted mean, standard deviation) • Linear Regression • Additional functions not found on the HP-38: - Subroutines, flags, loop control, random number, Pi, Log, x² and more Details: cuveesoft.ch/rpn38

Screenshots

Calca4 screens
RPN4 screens

Verdict

The call

The clearest difference is price: RPN at $1.99 against Calca's $9.99. RPN also leads on in-app purchases (none vs 2) and rating (5.0 vs 4.5). Calca's advantage is ratings volume (157 vs 7). On ads 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

Calca costs $9.99 and RPN $1.99 up front. Calca sells 2 one-off in-app purchases. RPN asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

RPN holds the better App Store score, 5.0 against 4.5. That said, the two scores are not equally well evidenced: Calca has 157 ratings behind it against 7, so its average is the more settled of the two. Written reviews point the same way: 76% of Calca's written reviews are positive against 100% of RPN's.

UpkeepUpdate frequency

Calca ships an update every 5 months, RPN every 2 months. The most recent releases landed on October 26, 2026 and October 20, 2026 respectively.

Scorecard8 real differences · 2 level
Calca versus RPN: the parameters behind the verdict, then further details
ParameterCalcaRPN
Price$9.99$1.99 — better
Rating4.5 (157 ratings)5.0 (7 ratings) — better
Positive reviews76.5% of reviews100.0% of reviews — better
Number of ratings157 — better7
Update frequencyEvery 5 monthsEvery 2 months — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases — betterPaid
DevicesiPhone, iPad, iPod — betteriPhone, iPod
Requires iOS15.012.0 — better
Further details — not scored
Size78 MB12 MB
Age rating4+4+
DeveloperKrueger Systems, Inc.CuVee Software

Customer experience

Calca

All ratings153 ratings
Positive87.6%
Neutral4.6%
Negative7.8%
Written reviews170 reviews
Positive76.5%
Neutral7.1%
Negative16.5%

RPN

All ratings6 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews4 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Bugs and requests

Calca

Reported bugs

12 issues
  • Magic Keyboard causes number input to overwrite instead of append
  • Text selection before numbers triggers increment/decrement instead of selecting
  • Cursor jumps forward and backward with external keyboards
  • iPad Pro keyboard truncation in portrait mode
  • Arrow key (=>) doesn't work in landscape mode
Show 7 more
  • App crashes on startup on some devices
  • File saving is temperamental and causes data loss
  • Folders don't persist unless calculations created within them
  • Large number calculations lose precision (10^100 + 1 - 10^100 returns 0 instead of 1)
  • Keyboard focus issues on iPad with Magic Keyboard
  • iOS 13+ button adaptation issues
  • Spinning beach ball on very large calculations

Requested features

15 requests
  • Files app and document browser integration
  • Dropbox and Google Drive support
  • Date calculation functionality
  • Looping and iteration support
  • User-defined function storage in separate files
Show 10 more
  • Temperature unit support (Celsius, Fahrenheit)
  • Logarithmic and non-proportional unit definitions
  • Multiple parametric plots simultaneously
  • Landscape mode optimization
  • Tabular data and multi-row markdown table support
  • Dark mode (now implemented)
  • Subscription model option for ongoing development
  • Decimal place formatting control
  • Charting and financial functions
  • Better document management interface

RPN

Not enough reviews yet to summarise bugs or requests.

In-app purchases

2 purchases

Calca

One-time2
  • 6-Month Optional Patronage$4.99
  • 12-Month Optional Patronage$7.99
None

RPN

No in-app purchases

Questions

Is Calca free?
Calca costs $9.99, and also offers in-app purchases.
Is RPN free?
RPN costs $1.99, with no in-app purchases.
Which has better reviews, Calca or RPN?
RPN is rated higher. Calca averages 4.5 out of 5 from 157 ratings, while RPN averages 5.0 from 7 ratings.
Do Calca or RPN have ads?
Neither Calca nor RPN shows ads.
Which is updated more often, Calca or RPN?
Calca ships an update every 5 months, and RPN every 2 months. Most recently, Calca was updated on October 26, 2026 and RPN on October 20, 2026.

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