You should reconsider the specifications for your garage door if you have multiple vehicles or a large vehicle to park inside.
Normal height of garage door.
Double garage doors have a width of 12 to 16 feet.
2 a double door.
For a garage attached or detached from your house of around 18 x 24 feet most popular width for a garage door is 16 feet.
Then the garage door would be 6 x 6 6.
Double car garage doors typically start at 12 feet wide and move.
Rv garage doors are taller with a height of 8 to 9 feet and width of 16.
Standard garage door sizes range from single doors to commercial doors.
For a shed the best size for installing a garage door is 8 x 14 feet.
As for the height it is 7 or 8 feet.
Custom doors range per home.
Measure the backroom the distance from the garage door opening to the back wall of the garage.
This is for a normal home with a normal car truck suv or van parked inside.
For an approximately 12 x 22 detached garage or one attached to your house the most common width is 8 or 9 feet as for the height it is 7 or 8 feet however in terms of height it can go up to 12 feet to accommodate an rv.
Use a step ladder to more easily measure the ceiling height.
If you have an rv the door can go up to 10 feet.
A garage will need backroom that equals the door height plus 18 inches and possibly more based on the installation of an automatic garage door opener.