VKCalc

While all computers come with all sort of predefined applications that you could use in order to work on your projects, not all of them have advanced features.
Still, the Internet offers many alternatives that you could check out. One of them is VKCalc. It's a neat software solution that helps you make calculations on your computer.

Simple and clean user interface

The application doesn't require any installation, which means that it won't take up any space on your system. It sports a really intuitive and clean graphical interface that makes it easy to navigate through multiple sections.
It even comes with some customization options, you can adjust the foreground and background color inside the program.

Make all sort of calculations

The program can directly evaluate mathematical expressions in the common infix notation. It operates with a single type of mathematical object, a complex number composed of two native floating-point values.
This means that you can make various mathematical calculations, but it does impose some restrictions. You won't be able to calculate matrices or fractions. Still, it supports many common mathematical functions and physical constants.
You can define custom variables and functions as well, and even load the custom quantities automatically at program startup. Identifiers can be set in Greek, Cyrillic and other Unicode characters.

Additional features and tools

The calculator can evaluate more than one formula in single run. Each formula goes on a separate line of the upper text box. Multiplications and divisions are performed before additions and subtractions, so you should use brackets.
Various common multiplication signs can be used and in unambiguous cases the sign can be omitted altogether. You can save results in a document on your computer.
All in all, VKCalc is a very useful application for performing all sort of mathematical calculations on your computer and saving results in a separate document.