There is no one “best” calculator app for iPhone, but there are some excellent options available. Of these, Paid app Calc seems to be the most popular and best rated. It offers a range of features and is very user friendly. Other good options include the free apps Scientific Calculator and Keylab Express. For those who need to use a calculator for more complex calculations, or who want access to a wider range of functions, might prefer apps like Apple’s built-in Calculator or iCalc Pro.