Maxima - Maxima is a fairly complete computer algebra system written in Lisp with an emphasis on symbolic computation.
Numi App - Numi is a beautiful text calculator for Mac.
Xoctave - The Affordable Matlab alternative which makes you save money. Xoctave is a powerful software that is meant to unleash the power of GNU Octave by creating a complete scientific computing environment.
SpeedCrunch - SpeedCrunch. SpeedCrunch is a high-precision scientific calculator featuring a fast, keyboard-driven user interface. It is free and open-source software, licensed under the GPL. Download Documentation Donate .
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.