Is there a workaround when Finder spends forever "calculating size"?

Solution 1:

The amount of time it takes is proportional to the number of files in the folder. If there are a lot of files, it will take a long time to calculate.

You can also try doing it from the Terminal like so:

du -sh /path/to/folder

Solution 2:

Sometimes it never stops. The process gets stuck sometimes. I use Daisy Disk from the Mac App store to calculate sizes and see where my hard drive space is used.

Solution 3:

This might not directly answer your question, but OmniDiskSweeper is quite a good tool for finding the big files on your hard disk.And the best thing is it is free. This is description from their wesbite.

OmniDiskSweeper is really great at what it does: showing you the files on your drive, in descending order by size, and letting you delete them easily! It scans your disks as quickly as possible and shows you the facts — if a file doesn't make the cut to stay, just click the big Delete button and be done with it. It's a fast, easy way to find those large files cluttering up your drive and clearing them out for new, better things. Make sure you want them gone, though. There's no going back.