I also found a command for directory size.
However, its default behaviour is to show the size of files recursively. So, I do not get the size of the folders in the directory I am interested in. Instead, I get the size of files within those folders and recursively so forth. I needed to set the depth of search into the folders. I found a parameter with a similar name. The following command works just as I need.
du --max-depth=1 -h