Your iPhone or iPod comes with its own capable calculator; turn it on its side, and it even knows trigonometry. But when you need more hardcore scientific or engineering functions, turn to PCalc. It includes an optional two-line display, multiple undo and redo, unit conversions, quick lookup of common constants, support for binary, octal, and hexadecimal number systems, and (believe it or not) much more. PCalc handles all the math you can muster.

Hot Number: Flip Pcalc on int side to see more functions. Tap the 2ed button to se the app’s trig and log functions. Tap 42 to insert constants, tap Tape to view your history or tap AB to do unit conversions. You can even change the calculator’s look and sound with custom skins.

Death and Taxes: Many things and constant in life, especially in science and math, PCalc offers an easy way to insert common constants into your calculations, all of them organized into logical categories. Tap the constant to add its value to the calculator’s digital display.