How to show actual size and allocated size on disk of a file in Ubuntu?
I can only answer for command line.
To show the actual size of the file:
du -b "file"
To show the allocated size of the file on disk: (= actual size rounded up to whole block size)
du -B 1 "file"
If you use PCManFM, you can do this in with a file manager in a GUI format.
It's right click menu, under properties - just where Windows puts it, if memory serves.
You should be able to install it with:
sudo apt install pcmanfm
Other file managers may offer the same functionality, but I know this one does. A quick check indicates that SpaceFM also offers the same.