PTC Mathcad is described as 'Software designed for engineering calculations, enabling data analysis and sharing of complex calculations. Offers productivity enhancements for product development' and is an app in the development category. There are more than 25 alternatives to PTC Mathcad for a variety of platforms, including Windows, Linux, Mac, Web-based and Android apps. The best PTC Mathcad alternative is SMath Studio, which is free. Other great apps like PTC Mathcad are Mathematica, Maxima, wxMaxima and Maple.
Free to commercial use. Interface is almost like Mathcad15.