Garage doors typically range from 9 feet to 20 feet wide and 7 feet to 8 feet tall. Popular widths for one-car garage doors are 8 feet, 9 feet or 10 feet, while those for two-car garage doors are 12 feet, 14 feet or 16 feet.
In existing structures, the size of the opening limits garage door dimensions. Measurements for a door include the height and width of the opening, the width of the space on each side of the frame and the headroom. The space between the top of the opening to the lowest part of the ceiling must be large enough for both the garage door tracks and the height of any planned automatic opener.
Filling extra space in a non-standard opening to fit a smaller door is not unusual; however, increasing an opening is more complex and sometimes requires lifting the roof or widening the garage.
In new structures, designing a garage requires many decisions, including how many vehicles need housing are their dimensions, including extensions such as mirrors and snow plows, and what storage is required for lawn mowers, tractors and snow blowers. After determining the space and storage requirements, making other design decisions is possible.