I hve a global shortcut to open a Julia REPL session and I use that to perform any sort of quick calculations instead of a GUI calculator. The best thing about this approach is that I can always create new functions for stuff I use often.
Qalc seems like a better calculator to me and is more stable somehow despite being written in I think C++. Not having to download a huge programming language taking up GB of space, research an ecosystem and import ten packages sounds ideal. I prefer python or R and sometimes even BC to Julia for terminal calculating anyways...
I'd let the post about qalculate be about qalculate here.