Comparison

Calca vs Obsidian

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

Obsidian

Organize your thoughts and ideas with a powerful knowledge base that utilizes local Markdown files. This app acts as your personal second brain, accessible on your mobile device for seamless note-taking and idea connection.

Highlights
  • Local Markdown file storage
  • Customizable toolbar
  • Graph view for connections
  • Community plugins
  • Themes
  • iCloud sync
Features
Read full description

Obsidian is a powerful knowledge base that works on top of a local folder of plain text Markdown files. It is a second brain, for you, forever. Now available on the go for iOS! Features include: - Customizable toolbar - Pull down quick actions - Graph view - Community plugins - Themes - Sidebar pinning for tablet - iCloud vaults

Screenshots

Calca4 screens
Obsidian4 screens

Verdict

The call

The clearest difference is price: Obsidian at Free against Calca's $9.99. Obsidian also leads on in-app purchases (none vs 2) and update cadence (every 3 weeks vs every 5 months). Calca's advantage is review sentiment (76% vs 62%). On rating, ads, device support and iOS requirement 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

Obsidian is free to download; Calca costs $9.99 up front. Calca sells 2 one-off in-app purchases. Obsidian asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 4.5 for Calca against 4.5 for Obsidian. That said, the two scores are not equally well evidenced: Obsidian has 2.7K ratings behind it against 153, so its average is the more settled of the two. Written reviews are what separate them: 76% of Calca's written reviews are positive against 62% of Obsidian's.

UpkeepUpdate frequency

Calca ships an update every 5 months, Obsidian every 3 weeks. The most recent releases landed on September 25, 2026 and September 24, 2026 respectively.

Scorecard7 real differences · 4 level
Calca versus Obsidian: the parameters behind the verdict, then further details
ParameterCalcaObsidian
Price$9.99Free — better
Rating4.5 (153 ratings)4.5 (2.7K ratings)
Positive reviews76.5% of reviews — better62.1% of reviews
Number of ratings1532.7K — better
Update frequencyEvery 5 monthsEvery 3 weeks — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
Best chart rank—#131 — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.0 — better15.6
Further details — not scored
Size78 MB38 MB
Age rating4+4+
DeveloperKrueger Systems, Inc.Dynalist Inc.

Customer experience

Calca

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

Obsidian

All ratings2,674 ratings
Positive85.6%
Neutral4.0%
Negative10.5%
Written reviews1,303 reviews
Positive62.1%
Neutral11.9%
Negative26.0%

User reviews

Calca

From 153 App Store ratings

What we love

  • 💡 Unique blend of text editor and calculator
  • 📝 Markdown support for documentation
  • 🔄 Dynamic recalculation of all values
  • ⚙️ Powerful mathematical and algebraic capabilities
  • 📊 Unit conversion and unit-aware calculations

Room to improve

  • 🐛 Magic Keyboard input bugs on iPad
  • ⚠️ Appears abandoned or poorly maintained
  • 🐛 Text selection issues with external keyboards
  • 📱 iPad landscape mode problems
  • 🐛 Cursor jumping and screen jumping during editing

Obsidian

From 2.7K App Store ratings

What we love

  • 🚀 Powerful features
  • 👍 Customizable and flexible
  • 🔒 Secure and private
  • 💡 Innovative note-taking approach
  • 🚀 Smooth mobile experience

Room to improve

  • 🐛 Sync issues and unreliable iCloud integration
  • 🔋 Slow startup and performance issues on mobile
  • 👎 Steep learning curve for new users
  • 👎 Limited sorting and organization options
  • 👎 Lack of WYSIWYG editing on mobile

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

Obsidian

Reported bugs

3 issues
  • Sync issues leading to data loss
  • Freezing and crashing on mobile devices
  • Editing bugs and text input issues

Requested features

5 requests
  • Improved sorting and organization options
  • WYSIWYG editing on mobile
  • Better integration with other cloud storage services
  • More intuitive onboarding process for new users
  • Native mobile widgets and share sheet integration

In-app purchases

2 purchases

Calca

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

Obsidian

No in-app purchases

Questions

Is Calca free?
Calca costs $9.99, and also offers in-app purchases.
Is Obsidian free?
Obsidian is free to download, with no in-app purchases.
Which has better reviews, Calca or Obsidian?
Calca and Obsidian are both rated 4.5 out of 5 on the App Store, from 153 and 2.7K ratings respectively.
Do Calca or Obsidian have ads?
Neither Calca nor Obsidian shows ads.
Which is updated more often, Calca or Obsidian?
Calca ships an update every 5 months, and Obsidian every 3 weeks. Most recently, Calca was updated on September 25, 2026 and Obsidian on September 24, 2026.

Other comparisons