Simple Calculator is a lightweight addon designed for Firefox that provides users with a straightforward interface for performing basic arithmetic operations. This tool is easily accessible via a toolbar button, allowing users to quickly open the popup UI and enter calculations directly. The calculator supports operations such as addition, subtraction, multiplication, and division, with results rounded to a maximum of seven decimal places for precision.

The addon also features an embedded virtual keyboard, making it convenient for users who prefer not to type using their physical keyboard. Simple Calculator is a subscription-based tool that enhances the personalization of the Firefox browsing experience by integrating a functional calculator directly into the browser. This simplicity and ease of use make it an ideal choice for users needing quick calculations while working online.