Tips for measuring a front door opening?
The only info you need to order a new door is the actual door measurement.  36"X81" for example.  The term rough opening refers to the actual stud frame opening which you cannot see or measure with the existing door jams and trim installed. If you are concerned if your rough opening is large enough, you will need to remove the interior trim to see exactly where the studs and leader are. The exterior trim (usually brickmold ) is usually part of the prehung unit and attached when you get the new door unit.