Common garage door dimensions
Of course, it's possible to have a garage door built with any dimensions. From 6 ft in three inch increments for the height. As to the width, it can be made within 1 inch increments.
But there are the most common garage door dimentions. Those standard width and height are normally used, in the main if premade doors are ordered.
Garage door dimensions are always given width first (i.e., 9x7 means 9 ft wide and 7 ft high).
Width. The most common dimensions are 8 ft and 9 ft for a single car garage door, 14 ft and 16 ft for a double car garage door. But doubles can range to 18 ft and sometimes beyond.
Height. 7 ft is the most popular height, premade doors are always 7 ft high. Currently 8 ft high garage doors becoming more popular as people often have got racks on top of their cars. Lots of recreational vehicles won't fit in 7 ft. That's why you'd better raise the height of your garage door to 8 or 9 feet and never think there's not enough height.
Garage depth. You need the depth of your garage to be at least 6.89 feet. That's necessary for a garage door opener to be installes and work properly. But average length of a car is 15 to 16 feet, that's why it is unlikely that you build a 5 feet deep garage.
And one more thing. Note that wide garage doors (i.e., 18 ft) can be made only for buildings in areas without high winds. If you want to choose such garage door dimensions, check the building codes first.