You can use the following snippet to check how much your tablespace is growing

Tablespace_Growth.sql

SELECT to_char(creation_time,
         'MM-RRRR') "Month", sum(bytes)/1024/1024/1024 "Growth IN GB"
FROM sys.v_$datafile
WHERE to_char(creation_time,'RRRR')='2014'
GROUP BY  to_char(creation_time, 'MM-RRRR')
ORDER BY  to_char(creation_time, 'MM-RRRR'); -----SELECT b.tsname tablespace_name,
         MAX (b.used_size_mb) cur_used_size_mb,
         ROUND (AVG (inc_used_size_mb),
         2) avg_increas_mb
FROM 
    (SELECT a.days,
         a.tsname,
         used_size_mb,
         used_size_mb - LAG (used_size_mb,
         1)
        OVER (PARTITION BY a.tsname
    ORDER BY  a.tsname, a.days) inc_used_size_mb
    FROM 
        (SELECT TO_CHAR (sp.begin_interval_time,
         'MM-DD-YYYY') days, ts.tsname, MAX ( ROUND ( (tsu.tablespace_usedsize * dt.block_size) / (1024 * 1024), 2)) used_size_mb
        FROM dba_hist_tbspc_space_usage tsu, dba_hist_tablespace_stat ts, dba_hist_snapshot sp, dba_tablespaces dt
        WHERE tsu.tablespace_id = ts.ts#
                AND tsu.snap_id = sp.snap_id
                AND ts.tsname = dt.tablespace_name
                AND sp.begin_interval_time > SYSDATE - 7
        GROUP BY  TO_CHAR (sp.begin_interval_time, 'MM-DD-YYYY'), ts.tsname
        ORDER BY  ts.tsname, days) a) b
    GROUP BY  b.tsname
ORDER BY  b.tsname;