SELECT cNmColuna = C.name
,cTpColuna = UPPER(TYPE_NAME(C.user_type_id))
,iMaxDigit = CASE
WHEN T.precision = 0
THEN C.max_length
ELSE T.precision
END
FROM sys.all_columns C WITH(NOLOCK)
INNER JOIN sys.types T WITH(NOLOCK) ON T.user_type_id = C.user_type_id
WHERE C.object_id = Object_Id('Nome da Tabela')
Ref: https://pt.stackoverflow.com/questions/12549/como-pegar-o-tamanho-total-de-caracteres-de-uma-coluna-sql