Oracle Database Discussions

okay, I am a little confused here. I have been searching the web and looking at a lot of documents. What I basically want to find out is this, how do I calculate the difference between the number of bytes a table is using and the total bytes allocated to a table space (going that way to get percent free for a particular table). So I need a byte count of a table and total table space and the percentage difference. I have been looking at the DBA_TABLES DBA_TABLESPACES and DBA_SEGMENTS views. I have tried to calculated the space as num_rows * avg_row_len (if I am wrong, let me know). I have been trying to compare that calculation to the number in DBA_TABLESPACES and DBA_SEGMENTS. I am just looking for the total space allocated to the table space that the table sits in (seem logical right now) to make the percentage value work. Thus I want to be able to track the table as it grows as compated to the table space it sits in to see a value as it changes over time (days, weeks, etc.) each time I run this script I am working on.

Can someone get me straight and help me to find out if I am looking in the right places. Any advice would help.

Edward