If you're a long-time KDE user, then you already know what the K at the start of KCalc's name stands for. KCalc is a powerful open-source desktop calculator that's (mostly) built for the KDE ecosystem.

To quote the app's official page, it "has everything you would expect from a scientific calculator...," and I have to say, I totally agree.

For starters, I have to point out that KCalc has four modes: Simple, Science, Statistic, and Numeral System mode. This alone makes it perfectly suitable for a wide range of users.

In short, the app can be as simple as a basic calculator desktop app, but it can also help you calculate trigonometric functions, perform logic operations, as well as statistical calculations.

One somewhat rare feature is that the app stacks results (somewhat of a History feature). This means that it's remarkably easy to recall previous calculation results in seconds.

You're also provided with some of the most famous Constants in Maths (Pi, Euler Number, Golden Ratio), Electromagnetism (Light Speed, Elementary Charge, Impedance of Vacuum, Permeability of Vacuum, Permitivitty of Vacuum),  and Atomic and Nuclear (Planck's Constant, Elementary Charge, Fine-Structure Constant).

The app can add constants in Thermodynamics (Boltzmann Constant, Atomic Mass Unit, Molar Gas Constant, Stefan-Boltzmann Constant, and Avogadro's Number), as well as Gravity (Gravitational Constant and Earth's Acceleration).

Just like all "K" apps, KCalc benefits from the same consistency and sublime KDE integration. What I mean by this is that it looks and feels like a K app. This also means that it's remarkably configurable (as most of these tiny KDE apps are).

For instance, you can change the font, and the display colors, but you can also add your own custom constants. To conclude, KCalc is a perfectly adequate and useful little calculator app that gets the job done flawlessly, no matter what your DE of choice is (as it can be installed on most distros directly from Flathub).