SQL Server file used space

gistfile1.txt

-- This is captured from SSMS (shrink file dialog)

use [yourDatabase];
select s.Name, CAST(CASE s.type WHEN 2 THEN s.size * CONVERT(float,8)
                               ELSE dfs.allocated_extent_page_count*convert(float,8) END AS float) AS [UsedSpaceKB]
      ,CASE s.type WHEN 2 THEN 0
                          ELSE 5120 - dfs.allocated_extent_page_count*convert(float,8) END AS [AvailableSpaceKB]
from            sys.filegroups             AS g  
inner join      sys.database_files         AS s   on ((s.type = 2 or s.type = 0) and (s.drop_lsn IS NULL)) AND (s.data_space_id=g.data_space_id)
left outer join sys.dm_db_file_space_usage as dfs ON dfs.database_id = db_id() AND dfs.file_id = s.file_id