If you’re going to keep your cars or trucks in the garage, you need it wide enough to open the doors and walk around the front of the cars. The challenge when building a garage additions is our cars and trucks are much bigger.
Everyone has different ideas about the type of car/truck you should use to size your garage. Not being an expert on cars and trucks, I found this helpful table at ConsumerReports.org. You need to identify three measurements – maximum car/truck length, width and height. Ceiling height is key for larger trucks which are much taller than the average car, affecting building height as well as the size of your garage doors (width and height).