How to get file sizes of large files in OS X Terminal?
Say you are looking for big files in your home directory, use this command:

find ~ -size +1G


Replace ~ with the directory of interest.

Update

My original response was wrong, but I'll keep it to remind myself. If you are trying to get the size of a file, try this:

stat -f '%z' filename  # Normal file
stat -L -f '%z' filename  # symbolic link file


I have not figure out how to do it for a directory yet.