How to Measure for a New Garage Door
To measure for a new garage door, measure the width and height of the rough opening (the finished hole in the wall, not your existing door), taking each at its widest and tallest point. Then measure the three clearances around the opening: side room, headroom, and backroom. Record all five numbers in inches — they determine both the door size and the spring-and-track system your garage can handle.
Step by step
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1
Measure the opening width and height
Stand inside the garage and measure the width of the opening from one side of the masonry or framing to the other, then the height from the floor to the top of the opening. Measure each in two or three spots and use the largest reading — openings are rarely perfectly square. A standard single door is about 8 or 9 feet wide by 7 feet tall; a double runs 16 feet wide. Round to the nearest inch and write both numbers down (width x height).
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2
Measure the side room
Side room is the flat wall space to the left and right of the opening, measured from the edge of the opening to the nearest wall or obstruction. You need a minimum of 3.75 inches on each side to mount the vertical track; 5.5 inches is comfortable for most systems. If a wall, light switch, or framing crowds one side, note exactly how much you have — it decides whether standard hardware fits.
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3
Measure the headroom
Headroom is the space between the top of the opening and the ceiling (or the lowest obstruction, like a pipe or light). Standard torsion-spring systems need about 12 inches; extension springs need around 10. If you have less, low-headroom track kits exist but must be specified up front. Measure to the lowest thing hanging down, not just the bare ceiling.
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4
Measure the backroom (how far the door tracks run back)
Backroom is the depth from the opening straight back into the garage along the ceiling, where the horizontal tracks and open door will sit. The rule of thumb is the door's height plus 18 inches — so a 7-foot door wants roughly 8.5 feet of backroom. If you have a garage door opener, add about 18 more inches for the rail and motor unit.
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5
Note the headroom-mounting surface and any obstructions
Look at what's actually around the opening: exposed framing vs. finished drywall, a sloped or low ceiling, ductwork, plumbing, or a wall that ends short of the opening. Snap a few phone photos and jot down anything within a couple feet of the opening. These details affect bracket placement and whether you need special hardware, and they're easy to forget once the installer arrives.
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6
Write up your measurement sheet
Put all five numbers on one sheet: opening width, opening height, side room (left and right), headroom, and backroom — all in inches. Add notes on your spring type (torsion bar above the opening, or extension springs running along the side tracks) and whether you have an opener. This single sheet is exactly what you'll hand a supplier or installer to get an accurate quote without a second trip.
When to call a pro
Call a pro if you have less than 3.5 inches of side room or under 10 inches of headroom, if your ceiling slopes or has obstructions, or if you're replacing a torsion-spring door — getting the size or hardware clearance wrong is expensive, and a free in-home measure removes all the guesswork.
Call (888) 290-7421Frequently asked
Do I measure the old door or the opening?
Measure the opening — the finished hole in the wall — not your existing door. Garage doors are sized to the opening they cover, and the door panel itself is slightly larger than the hole. Measuring the old door usually gives you a number that's an inch or two off, which can mean ordering the wrong size.
What is a standard garage door size?
For a single-car door, 8 ft x 7 ft and 9 ft x 7 ft are the most common. Double-car doors are typically 16 ft x 7 ft. Taller 8-foot doors are common in newer homes and where people park trucks or SUVs. If your opening doesn't match a standard size, doors can be made to order — just confirm the exact opening measurements first.
How much clearance do I actually need around the opening?
As a baseline: at least 3.75 inches of side room on each side, about 10 to 12 inches of headroom above the opening (12 for torsion springs, 10 for extension), and backroom equal to the door height plus 18 inches. Add roughly 18 inches of headroom and backroom if you're installing or keeping a powered opener. Tight on any of these? Low-clearance kits exist, but they have to be ordered up front.
Can I just have someone measure it for me?
Yes, and for a torsion-spring door or any tight or unusual garage, that's the smart move. Garage Door Pros offers a free in-home measure where a tech confirms the opening size, checks all your clearances, and identifies the right spring and track system — so the door fits the first time and you avoid paying for a re-order. Give us a call and we'll set it up.
Rather leave it to a pro?
Licensed local techs, same-day service, upfront pricing, and a 1-year warranty.