Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.

Soulver - Soulver is a software application that functions as a calculator that allows you type a continuous stream of information rather than having to input data into multiple cells.

NumWorks - The graphing calculator that makes learning math easier.

RealCalc Scientific Calculator - RealCalc Scientific Calculator

SpeQ Mathematics - SpeQ is a small, extensive mathematics program with a simple, intuitive interface.

GetBricksApp - Bricks is a note-taking web app with a built-in calculator. It can be installed as a desktop or mobile app, because of PWA technology this app built with. Which is also makes it offline available. Notes created with Bricks can be shared.