Calcute

Since it is designed for performing only basic operations, Windows' default calculator lacks many advanced functions.

This free and light calculator has many of the same functions that a scientific calculator has. For example, you can calculate algebraic functions like sine, cosine, tangent and more, as well as the standard arithmetic operations. The program lets you display your operations as if it was a physical tape calculator, thus allowing you to see every step of them, as well as making corrections and export the process and results via copy-paste. Or you can set it to display only the results in a single-line mode, as with any pocket calculator. By default, the program saves your current operations when you close it. This can be very useful since it prevents data loss when accidentally closing the program.
The program has a couple of disadvantages. One of them is its unattractive interface. Also, if you make any correction to a factor of the displayed operation, the program does not correct the entire operation, meaning that you will need to perform again the subsequent calculations to obtain the right result. Other than that, it is a good program that can be useful for many people. And the best part is that it is absolutely free.