How to find Table Size

I have lot of tables created and I wanted to find the table size of each. Is it possible to do this? What is the command or function used for finding this?

First go for..

analyze table tabe_name compute statistics;
and then give
select num_rows,blocks ,empty_blocks as
empty,avg_space,chain_cnt,avg_row_len from dba_tables
where table_name='table_name';
now
blocks * db_block_size = table size

how can it possible.any simple way to make understand me