One Calculator is a free Android application developed by Pierfrancesco Soffritti that offers a wide range of features. It includes a scientific calculator with RPN mode and calculation history, a graphing calculator, a unit converter, a number base converter, and a matrix calculator. Its Material Design and ease of use make it accessible to everyone. One Calculator is suitable for solving both basic and complex mathematical calculations.

The app includes a basic arithmetic calculator, definite integrals, trigonometric functions such as sin, cos, tan, arcsin, arccos, and arctan, complex numbers, RPN calculations using Reverse Polish notation/postfix notation, graphs for X,Y equations, and measurement unit conversion. Additionally, it offers conversion between decimal, hexadecimal, octal, and binary, as well as matrix calculus. One Calculator has an interactive chronology of operations and specialized warning of errors. The app supports both smartphone and tablet devices and offers a range of themes.