In Google Spreadsheet, is there a way to conditionally format a cell if it has more than 30 characters?
Not on the cell itself, without the usage of Google Apps Script. Adding a helper column will allow you get realy close:
Now add the following formula in
This will check column A, whether the entry has more than 30 characters and will return TRUE or FALSE.
See example file I've prepared: more than 30 characters
If your cell is A1, in New Google Sheets, in Custom formula is please try: