Calca vs Obsidian
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
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.
- Symbolic calculation
- Equation solving
- Expression simplification
- Markdown text editor
- Real-time updates
- Unit and currency conversion
- Matrix operations
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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!
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.
- Local Markdown file storage
- Customizable toolbar
- Graph view for connections
- Community plugins
- Themes
- iCloud sync
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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
Verdict
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
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.
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.
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.
| Parameter | Calca | Obsidian |
|---|---|---|
| Price | $9.99 | Free — better |
| Rating | 4.5 (153 ratings) | 4.5 (2.7K ratings) |
| Positive reviews | 76.5% of reviews — better | 62.1% of reviews |
| Number of ratings | 153 | 2.7K — better |
| Update frequency | Every 5 months | Every 3 weeks — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | Free — better |
| Best chart rank | — | #131 — better |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.0 — better | 15.6 |
| Further details — not scored | ||
| Size | 78 MB | 38 MB |
| Age rating | 4+ | 4+ |
| Developer | Krueger Systems, Inc. | Dynalist Inc. |
Customer experience
Calca
Obsidian
User reviews
Calca
From 153 App Store ratingsWhat 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 ratingsWhat 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
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- 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
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- 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
Calca
- 6-Month Optional Patronage$4.99
- 12-Month Optional Patronage$7.99
Obsidian
No in-app purchases









