You can create an Editor Utility Widget that can do the calculations for you.
Here’s what I came up with. It’s crude, but gets the job done. You can modify it as you like:
Scale is by default a multiplier, basically. So, values of X, Y, and Z are not in Unreal Units, instead as a value multiplying by the mesh’s / actor’s original size in the actual units (whether Unreal Units, cm, or meters, etc). How do I set the details panel scale values to be in actual units? So, if I have a mesh that’s 100x100x100, then I would enter those exact values for cm / uu rather than entering 1 for each, or to get it bigger having to enter a fraction or multiplier number. It’s more time-consuming and disruptive trying to calculate the exact decimal number I need to enter to get the actor to resize for fitting and building and all that.