Showing the file size in Archiva

I was talking with a user recently who needs to know the exact size of
the artifacts in Archiva.

I'm vaguely aware that file sizes differ depending on how they are
calculated (number of bytes in the file vs. how much space it takes up
on disk?).  He's looking to compare the 'original' size from Archiva
to the file size reported by a tool that scans the production web
servers, and it would need to match.

Could this be displayed easily?  What would be involved?

--
Wendy