Determining Free Space Per SQL Server Database

SELECT DB_NAME(database_id) AS DatabaseName,
CAST([Name] AS varchar(20)) AS NameofFile,
CAST(physical_name AS varchar(100)) AS PhysicalFile,
type_desc AS FileType,
((size * 8)/1024) AS FileSize,
MaxFileSize = CASE WHEN max_size = -1 OR max_size = 268435456 THEN 'UNLIMITED'
WHEN max_size = 0 THEN 'NO_GROWTH'
WHEN max_size <> -1 OR max_size <> 0 THEN CAST(((max_size * 8) / 1024) AS varchar(15))
ELSE 'Unknown'
END,
SpaceRemainingMB = CASE WHEN max_size = -1 OR max_size = 268435456 THEN 'UNLIMITED'
WHEN max_size <> -1 OR max_size = 268435456 THEN CAST((((max_size - size) * 8) / 1024) AS varchar(10))
ELSE 'Unknown'
END,
Growth = CASE WHEN growth = 0 THEN 'FIXED_SIZE'
WHEN growth > 0 THEN ((growth * 8)/1024)
ELSE 'Unknown'
END,
GrowthType = CASE WHEN is_percent_growth = 1 THEN 'PERCENTAGE'
WHEN is_percent_growth = 0 THEN 'MBs'
ELSE 'Unknown'
END
FROM master.sys.master_files
WHERE state = 0
AND type_desc IN ('LOG', 'ROWS')
ORDER BY database_id, file_id