Mathematica
Commercial
Wolfram Mathematica (usually termed Mathematica, Mathematica software suite) is a mathematical symbolic computation program.
fxSolver
Free
fxSolver is a math solver for engineering and scientific equations.
Swift Calcs
Free
Swift Calcs enables users to effortlessly create and collaborate on interactive computational documents, from any device.
Sage
Open Source
Sage offers business management, bookkeeping & accounting software to meet any business need, from small to midsized businesses.
Matplotlib
Open Source
Matplotlib is a plotting library for the Python programming language and its numerical mathematics extension NumPy.
SMath Studio
Free
SMath Studio is a freeware, closed source, mathematical notebook program similar to Mathcad.
Compare MATLAB with alternatives
Compare SMath Studio and MATLAB and decide which is most suitable for you.