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.
Normal height of garage door.
Then the garage door would be 6 x 6 6.
For a shed the best size for installing a garage door is 8 x 14 feet.
You should reconsider the specifications for your garage door if you have multiple vehicles or a large vehicle to park inside.
Standard single car garage door widths start at 8 feet for single car garages and move up in 12 inch increments to 10 feet wide.
Custom doors range per home.
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.
2 a double door.
If you have an rv the door can go up to 10 feet.
This is for a normal home with a normal car truck suv or van parked inside.
Standard garage door sizes range from single doors to commercial doors.
Single garage doors are a height of 7 feet with widths from 8 to 10 feet.
Double car garage doors typically start at 12 feet wide and move.
Use a step ladder to more easily measure the ceiling height.
Measure the backroom the distance from the garage door opening to the back wall of the garage.
Double garage doors have a width of 12 to 16 feet.
As for the height it is 7 or 8 feet.