How can I see a folder's exact size in bytes?

Question

I have a folder with 40 GB of dozens of directories and stuff, and I want to see the exact size of the root folder in bytes ..

I have tried using this, but it shows the size in kilobytes:

du -s foldername

Answer 1

Use the -B1 parameter to du:

du -s -B1 foldername

$ man 1 du
 -B, --block-size=SIZE
          use SIZE-byte blocks

You could also try the --apparent-size flag