The Statistics page gives an overview of the size, both on-disk and in the database, of a repository.

Details listed include:

Revisions	The number of revisions in this repository's complete history. In other words, a count of the number of commits (whether automatic or manual) which have occurred.
Folders	The number of top- and sub-level folders in the reposity tree.
Files	The number of files in the repository tree.
Tree Size	The combined size of all files in the repository (based on the latest revision).
Disk Space Needed	An estimate of the disk space needed to store a copy of the entire latest revision of the repository's files.
Database Size	The size of the repository's database structure, including all history, previous revisions, shares, etc.