Following Scripts will calculate rowsize for every table.
;with cte as (
FROM SYS.COLUMNS SysCol inner join sys.tables SysTab on SysCol.object_id = SysTab.object_id
FROM SYS.INDEXES SysInd INNER JOIN SYS.TABLES SysTab ON SysInd.OBJECT_ID = SysTab.OBJECT_ID
inner join sys.columns SysCol on SysCol.object_id = SysTab.object_id
inner join sys.index_columns IC on SysCol.object_id = IC.object_id
and SysCol.column_id = IC.column_id ) a
group by a.name
select TableName, SizeInBytes, case when SizeInBytes>8060 then 1 else 0 end Spill from CTE.
There is an additional column by name Spill in case the row size is exceeding 8060 bytes which is max a page can hold, anything beyond that will need that record to be accommodated in another page.
Refer to http://sqlnuts.com/2015/09/05/sql-server-understanding-data-density/ to know more about page.