SpeedCrunch is great too, it was originally inspired by the WinXP PowerCalc - probably the best calculator from Microsoft: http://dan.hersam.com/2010/11/10/powercalc-in-windows-7/ (SpeedCrunch still lacks the graph rendering part, though has other features and improvements)
Re:%*$*#&#* Windows 7 Calculator
by RadioactiveMan on Friday December 25, 2015 @01:02PM
(#10791810)
I adore SpeedCrunch. I don't have fancy large number requirements but I love the interface. It works on Linux too, though I think it's an old version in the Ubuntu repository so you might prefer to download the source instead.
https://bitbucket.org/heldercorreia/speedcrunch