Comparison

Calca vs ModTest Pro

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

ModTest Pro

Features
Read full description

MODTest Pro is a fast and simple utility for testing MODBUS devices over WiFi or Bluetooth. It supports a wide range of MODBUS functionality, including the ability to operate as a client or server (master or slave). It supports both TCP and UDP connections when using WiFi and it supports serial communication via many BLE modules equipped with Bluetooth 4 or higher that provide UART bridging capability. Tap the Setup button to enter the appropriate parameters for your device. Return to the main display to send your poll and view the data (when in client mode) or accept and respond to data requests from a master device (when in server mode). The Comm Setup view allows a number of addressing, timing, and communication mode parameters to be configured. Besides a comprehensive user guide, the app also has extensive built-in help. Tap on any yellow label or info button for a description of that parameter. The app supports MODBUS-TCP, -RTU, and -ASCII protocols, and they can all be transmitted via TCP, UDP, or Bluetooth. It also supports the GSI protocol which was developed in 1985 and was the first tank gauging protocol to use standard RS232/RS485 serial data communication. The app also features a User Data Mode that allows you to enter a complete poll string independent of any particular protocol. This allows transmission of special ASCII data polls or any MODBUS command that is not natively supported by the app. The following MODBUS function codes are supported: 1 – Read Coils 2 – Read Discrete Inputs 3 – Read Holding Registers 4 – Read Input Registers 5 – Write Single Coil 6 – Write Single Register 7 – Read Exception Status 15 – Write Multiple Coils 16 – Write Multiple Registers 17 – Report Server ID Addresses must be entered in standard MODBUS format (0-65535). If you are accustomed to specifying register addresses in "Modicon format", simply subtract 1 from the Modicon Address and delete the prefix number. For example, Modicon Holding Register 40101 is equivalent to MODBUS address 100. The app supports a wide range of data representations including: Unsigned Integer: 16 bit, 32 bit, and 64 bit Signed Integer: 16 bit, 32 bit, and 64 bit Floating Point: 32-bit, and 64-bit using IEEE-754 specifications Hex Data Strings: 16-bit, 32 bit, and 64-bit Bit and Byte Representations for Coils & Discrete Inputs The app also supports the following "reverse modes" of floating point data storage: Atomic 8-bit Little Endian Atomic 16-bit Little Endian PDP Endian Bit Reversal When you exit the Comm Setup page, WiFi connections will be established automatically; however, a manual scan must be initiated to find and select a BLE module within range in order to establish a Bluetooth connection. After a successful Wifi or BLE connection, simply tap the Start Poll button to send your poll command (when in client mode). Continuous polling is also supported. When in server mode, the app will wait for and respond to poll requests from a master device once a WiFi or BLE connection is made. The app scans for UART Service & TX/RX Characteristic UUIDs from BLE devices by a number of manufacturers. The UUIDs that are supported are detailed in the app User Guide. A communication status window will show the raw byte strings that are sent to and received from a remote device. Received data will also be shown in tabular form when in client mode and communication events will be shown when in server mode. The app also tracks a number of communication statistics. When using WiFi your device must be on the network as the device that you want to test. Be sure to use the Settings app to configure your network settings before using the app or you will surely get socket connection errors. The app contains no ads or in-app purchases and we will never nag you for reviews, although we do appreciate them. If you have any issues with the app, please send us a message before posting a negative review and give us a chance to address your concerns.

Screenshots

Calca4 screens
ModTest Pro4 screens

Verdict

The call

The clearest difference is in-app purchases: ModTest Pro at none against Calca's 2. ModTest Pro also leads on update cadence (every 2 months vs every 5 months) and iOS requirement (13.0 vs 15.0). On price, 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 ModTest Pro $9.99 up front. Calca sells 2 one-off in-app purchases. ModTest Pro asks for nothing beyond the download.

UpkeepUpdate frequency

Calca ships an update every 5 months, ModTest Pro every 2 months. The most recent releases landed on November 1, 2026 and October 31, 2026 respectively.

Scorecard3 real differences · 7 level
Calca versus ModTest Pro: the parameters behind the verdict, then further details
ParameterCalcaModTest Pro
Price$9.99$9.99
Rating4.5 (157 ratings) — better—
Positive reviews76.5% of reviews—
Number of ratings157 — better—
Update frequencyEvery 5 monthsEvery 2 months — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.013.0 — better
Further details — not scored
Size78 MB26 MB
Age rating4+4+
DeveloperKrueger Systems, Inc.Dohmann Engineering Services

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

ModTest Pro

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

ModTest Pro

No in-app purchases

Questions

Is Calca free?
Calca costs $9.99, and also offers in-app purchases.
Is ModTest Pro free?
ModTest Pro costs $9.99, with no in-app purchases.
Do Calca or ModTest Pro have ads?
Neither Calca nor ModTest Pro shows ads.
Which is updated more often, Calca or ModTest Pro?
Calca ships an update every 5 months, and ModTest Pro every 2 months. Most recently, Calca was updated on November 1, 2026 and ModTest Pro on October 31, 2026.

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