The text within a concrete5 website is stored within blocks, and the data for those blocks is stored within the database.

What you'll find is that this text really doesn't take much space it all, compared to images and documents. Even just one image could be larger the the total amount of space all of your site's text content takes up.

The best way to find the total space your site takes up is by finding that figure at the server level, not at the concrete5 level. If you have something like cPanel access, in that you could find lots of information about the disk usage, basically giving you a total.

There is the total size for your website's files (so concrete5's files, plus the files you've uploaded), plus the size of the data in the database. Concrete5 databases can get large-ish, but they're generally no more than 5-10 meg.

I believe that the file storage location need not necessarily be located within the c5 directory (and maybe not even within public_html). Moreover, there can be more than one file storage location. So, if you've got a customised installation, you might need to check the file storage location(s) as well.