How to Measure Garage Doors

Most homeowners don’t know how to measure garage doors properly. It is important to take precise measurements as mistakes can cost you time and money. Never rely on panel count or estimation as each opening is unique. Use the list of key measurements below before ordering or installing a garage door. Perimeter weather seal (vinyl door stop) will provide a one inch cushion in the case of minor imperfections.

Door Width

Measure the width of the opening at the widest point. Take measurements from both ground level and eye level – in case the frame is out of square. You will be measuring how wide the door is from one side of the opening to the other. To prevent splitting and unsafe conditions residential doors are best framed with 2″ x 6″ wood. Look for openings that are out of square and weak, rotting boards. Never install a garage door on an unsafe door frame.

Door Height

Measure the height of the opening at its highest point. Be sure to look for irregularities in the floor. An unlevel floor may require wider bottom seal on the door or the use of adjustable bottom retainer. Always be sure to inform the home owner of un-level flooring as water leaks may be a problem.


Measure the horizontal space on the side of the openings. A minimum of 4 inches is recommended for standard 2 inch bracket mount vertical track. Jackshaft openers, that mount on the side of the door require up to 10 inches of space on one side of the door.


The space between the top frame of the garage door and the ceiling (or closest obstruction) is known as headroom. With standard lift, 12 inch radius, bracket mount track 15 inches of headroom is needed. If you don’t plan on installing an automatic garage door opener 12 inches of space will be sufficient.

Minimum Headroom Requirements

If the current opening being measured doesn’t have enough space , special low-clearance track can be purchased. This track provides 3 inches of extra clearance. This means you will need 12 inches of headroom if you plan on using an automatic garage door opener. You will need only 9 inches of headroom if you don’t plan on using an automatic garage door opener. In cases where you don’t have at least 8-9 inches of headroom you will have to frame down the opening and install a smaller garage door that provides adequate headroom clearance.


Finally, you will need to measure the backroom in the garage. Measure the distance from the opening to the back of the garage or closest obstruction. Minimum backroom without the use of an automatic electric opener is 20 inches. If a garage door opener is installed the door height plus 56 inches is required.

Other Important Measuring Points


  • If you are measuring a job with an unfinished floor be sure to consult the contractor or homeowner to determine how high poured concrete will be. If you have to install the garage door before the flooring is finished you will have to cheat your vertical track to compensate. Always compensate for un-level flooring low spots in the concrete where water may leak into the garage.
  • Always ensure you have an electric outlet within reach of an automatic opener. Most electric openers come with a 4-foot power cord. Running an extension cord is not recommended.
  • Check all of the wood work in the garage. Ensure that the structure is sufficiently secure – taking note of split, warped or rotten boards. Again all wood work should be done with 2 x 6 boards.
  • Make sure vertical bucking extends 24 inches beyond the height of the door. End bearing plates must be fastened at the level of the spring line.
  • Make sure you have a spring pad for the center bearing plate and spring line to anchor into. This will be mounted in the headroom space in the center of the garage.
  • Take note of any impeding structure like duct work, pipes and electrical cords that may obstruct your garage door installation.

The most common garage door sizes are 8×7, 9×7 and 16×7. Never assume that a door is a common size – measure all doors yourself.