Kalkules 

Despite the broad use of computers in different activities, calculators are still used to perform certain calculations. This free program is a calculator that can make complex, non-conventional mathematical operations.

At first sight, the program looks like a beefed-up version of the old Windows 7 calculator. Nevertheless, if you look closer, you will find that it has much more features. For example, it has a unit converter, which is more functional than the one in Windows 10, since it includes units like nanometers and light years. You can also manage statistics, polynomials, function derivatives, function graphs, and more.

A good feature is a possibility of setting the interface to your mother tongue to make its use easier. The program includes more than a dozen of different languages, such as Spanish, Polish, Russian, French, and of course, English.

Taking into account that handheld calculators can be expensive and that this program is absolutely free, you may want to consider its use. Please note that if you find the program useful and want to contribute to its development, you can make a donation through the developer's website.