Since everyone has limited space and I use my calc by numpad (faster),
is there any calculator (or option to the Windows 10 calculator), to hide the on-screen keyboard (the buttons with numbers)?
You could use python from a terminal window. Small footprint with no keyboard. Keep a Python terminal at bottom of screen and just click it to use. The search engine Spotlight of the Mac also will do calculations. Maybe similar app on the windows will too. And Wolfram Alpha, a menu app, will do calculations as well using keyboard keys.