File size is the storage space required for storing a file and its entire subtree
without data deduplication.
See compressed size for the actual space required for storing a file or a website.
Effectively, it's the sum of the file's:
- property size,
- attribute size,
- body size,
- children size,
- linked file size for hash-based links,
- plus a little serialization overhead.
The file size adds up along the tree, thus it is easy to calculate.