How many blocks is my database
This is what you're looking for, if I've read your question correctly:

SQL&gt; select segment_type, sum(bytes)/1024/1024 as size_in_mb, sum(blocks) as size_in_blocks
  2  from dba_extents
  3  group by segment_type;

SEGMENT_TYPE       SIZE_IN_MB SIZE_IN_BLOCKS
------------------ ---------- --------------
LOBINDEX              43.4375           5560
INDEX PARTITION         61.75           7904
TABLE SUBPARTITION          2            256
TABLE PARTITION       70.6875           9048
NESTED TABLE           1.8125            232
ROLLBACK                .4375             56
LOB PARTITION         21.1875           2712
LOBSEGMENT              331.5          42432
INDEX                338.8125          43368
TABLE                   713.5          91328
CLUSTER                 60.25           7712
TYPE2 UNDO            14.3125           1832

12 rows selected.

SQL&gt;