Dúo Calculator
Scientific, units and history
Only for iPhone
$1.99 · Designed for iPhone. Not verified for macOS.
iPhone
Now compatible with and optimized for iPhone Duo: fold it for a basic calculator, unfold it for a full scientific one with programmer mode and a converter. New history.
Now compatible with iPhone Duo. LiquidCalculator is now Dúo Calculator: fold your iPhone Duo and it's a basic calculator; unfold it and it becomes a full scientific calculator.
On any iPhone: a basic or scientific keypad, a unit converter and your calculation history, with a precise math engine. No ads, no account and no in-app purchases.
ONE CALCULATOR, TWO SCREENS
• Folded: a basic calculator with big keys. In landscape, a compact scientific keypad appears (you can turn it off in Settings).
• Unfolded: a 10 × 5 scientific keypad with every function in view; with the screen flat, also programmer mode and a unit converter.
• Half open like a laptop, the result sits above the fold and the keypad below it. Open like a book, the keypad splits across both sides of the fold.
• Fold or unfold in the middle of a calculation and your work stays put: keys slide to their new places and the new ones appear.
• It also adapts to Split View on the inner display.
ON YOUR IPHONE
• Pick Basic or Scientific from the menu, in portrait or landscape.
• Unit converter and History on every model.
• iPhone SE and accessibility text sizes keep the big basic keys.
HISTORY
• Your last 50 calculations, newest first
• Tap a result to use it again; swipe to delete one, or clear them all
• On an unfolded iPhone Duo it opens in a panel that never crosses the fold
A REAL SCIENTIFIC CALCULATOR
• Trigonometry in degrees or radians, inverse and hyperbolic functions
• ln, log10, log2 and logarithms in any base
• Powers, roots of any degree, factorial, 1/x, π, e and EE notation
• Parentheses, memory (mc, m+, m−, mr) and the 2nd key
• Live result as you type, plus cursor editing: tap the expression to fix any point
It does not include graphing, matrices or statistics.
EXACT UNDER THE HOOD
Basic operations use exact fractions: 0.1 + 0.2 gives 0.3 and 1 ÷ 3 × 3 gives 1. Functions such as sin, ln or e^x are computed with 60 digits of precision and the display shows up to 16. Invalid operations, such as dividing by zero or tan 90°, show a clear error instead of a wrong answer. The engine is checked against an independent reference model on hundreds of test cases.
PROGRAMMER MODE (large screens, such as an unfolded iPhone Duo)
• 8, 16, 32 and 64-bit integers, signed or unsigned
• BIN, OCT, DEC and HEX at once, with a bit grid you can tap
• AND, OR, XOR, NOR, NOT, shifts, rotations, 1's and 2's complement, mod
UNIT CONVERTER
• 87 units in 11 categories: length, mass, temperature, area, volume, speed, time, data, energy, pressure and angle
• Swap units with one tap, pull in the calculator's value or send the result back to it
• Works offline; currencies are not included
YOUR WAY
• Light, dark or system theme, with optional pure OLED black
• Four accent colors: amber, indigo, mint and graphite
• Liquid Glass design; haptics and the aurora background are optional
• Copy and paste, plus hardware keyboard support
• English and Spanish, with VoiceOver labels; respects Reduce Motion, Reduce Transparency and Increase Contrast
PRIVATE BY DESIGN
• Collects no data: no account, no ads, no analytics, no tracking
• Never uses the network: the app never sends your calculations anywhere
• Settings, your last calculation and your History are stored on the device (and in its backups) and removed from it with the app
COMPATIBILITY
• Now compatible with and optimized for iPhone Duo, on both the outer and the inner display.
• Runs on any iPhone with iOS 26 or later. Programmer mode needs a large screen, such as the inner display of iPhone Duo.
• iPhone only.
Support and feedback: alex@nextechia.dev
iPhone and iPhone Duo are trademarks of Apple Inc. This app is independent and is not affiliated with Apple.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
LiquidCalculator is now Dúo Calculator: compatible with and optimized for iPhone Duo.
• On iPhone Duo: folded it's a basic calculator; unfolded, a full scientific one with programmer mode and a unit converter. Half open, the result sits above the fold.
• Scientific mode on your iPhone, too: pick it from the menu or turn your phone.
• Calculation history: tap a result to use it again.
• Unit converter on every iPhone.
• New design and a high-precision math engine.
History from the previous version isn't shown in this version.
The developer, Alejandro Hernandez Mitre, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Alejandro Hernandez Mitre
- Size
- 3.6 MB
- Category
- Utilities
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later. - Mac
Requires macOS 26.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.0 or later.
- iPhone
- Languages
- English and Spanish
- Age Rating
4+
- 4+
- Copyright
- © 2026 Alex Mitre
