Accurately sizing existing Tables

I am currently moving our production dB from a Unix box to an NT server
with a lot less available disk space.

In order to facilitate this move I need to shrink the tablespaces down to
a size nearer the true demands of the application.

I have constructed some queries based on DBA_FREE_SPACE, DBA_SEGMENTS etc.
but the values they provide are based on the number of extents allocated.
My predecessor created some of the tables (which are nearly empty) with
10Gb of an INITIAL EXTENT, similarly the other storage clauses are erratic
which makes my queries misleading.

There are too many tables to make a count(*) and sizing using the equations in the Administrators handbook feasible, so I was hoping that
somebody might know of a query/method/script which would generate a realistic/accurate space usage sizing for the existing tables and their
data.

thanks in advance,

regards,

Michael Walsh
mjwalsh_at_hotmail.com

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