Filter by filesize column and create a view

Hi

In a web application there is a document library and daily 1000 to 2000 documents are uploaded by users,

so here i want to calculate the average size of documents uploaded to this web application, so here i want to create a view based filesize column and apply filter on this column.

ex: filesize >500 KB

i did not fount filesize column in filter condition while i creating a view..i taken the 500 kb is for example. i will check in some range values like 500 - 1000 kb and 1000 - 2000 

adil