Dúo Calculator

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,