Here's a very simple way using sp_spaceused function

declare @tblname nvarchar(100)

Select @tblname = 'yyyyyyyyyy' -- put your table name here

declare @test-2 table(name varchar(100),numrows bigint, reserved nvarchar(1000),data nvarchar(1000),index_size nvarchar(1000),unused nvarchar(1000))

Insert...