Calculate the maximum number of character in a row for a column
Solution 1:
No extra column is needed, just one cell per column, within that column.
If the number of rows you have is set, you can use an array formula to determine the max length. The formula is =MAX(LEN(A2:A100)), confirmed with CtrlShiftEnter, where A2:A100 are your values. This tells Excel to evaluate the lenght (LEN) of all rows in the reference, then return the longest (MAX).
If your row count will change, you can use a Named Range to determine which cells will be evaluated, then use the defined Name in your Array formula.