I need to know how much disk space a table is using in SQL Server

CREATE TABLE #tmpSizeChar (
     table_name sysname ,
     row_count int,
     reserved_size varchar(50),
     data_size varchar(50),
     index_size varchar(50),
     unused_size varchar(50))                              

CREATE TABLE #tmpSizeInt (
     table_name sysname ,
     row_count int,
     reserved_size_KB int,
     data_size_KB int,
     index_size_KB int,
     unused_size_KB int)   

SET NOCOUNT ON
INSERT      #tmpSizeChar
EXEC      sp_msforeachtable 'sp_spaceused ''?'''     

INSERT INTO #tmpSizeInt (
        table_name,
        row_count,
        reserved_size_KB,
        data_size_KB,
        index_size_KB,
        unused_size_KB
        )
SELECT  [table_name],
        row_count,
        CAST(SUBSTRING(reserved_size, 0, PATINDEX('% %', reserved_size)) AS int)reserved_size,
        CAST(SUBSTRING(data_size, 0, PATINDEX('% %', data_size)) AS int)data_size,
        CAST(SUBSTRING(index_size, 0, PATINDEX('% %', index_size)) AS int)index_size,
        CAST(SUBSTRING(unused_size, 0, PATINDEX('% %', unused_size)) AS int)unused_size
FROM #tmpSizeChar   

/*
DROP TABLE #tmpSizeChar
DROP TABLE #tmpSizeInt
*/

SELECT * FROM #tmpSizeInt
ORDER BY reserved_size_KB DESC