Summary:
What You'll Need Before You Start
How to Measure for a New Garage Door in 5 Steps
Work through these in order. Each takes a couple of minutes, and together they give a supplier or installer the full picture.
Step 1: Measure the Width of the Opening
Measure straight across the opening at its widest point, frame to frame. Do it three times, though, at the bottom, middle, and top. Older openings are rarely square, and you want the largest of the three numbers. That’s your width.
Step 2: Measure the Height of the Opening
For height, run the tape from the floor to the top of the opening, again at the left, center, and right. Floors settle and headers sag, so these three often disagree. Record the tallest. A sloped floor usually shows up right here, and it affects how well the finished door seals.
Step 3: Measure the Side Room
Side room is the space on each side of the opening, between the frame and the nearest wall, where your tracks and springs mount. A standard setup needs at least 3.75 inches per side. Measure the two sides separately, because in a corner garage, one side often comes up short. If you’re planning a side-mounted opener, you’ll want more room on that side, so note which wall is which.
Step 4: Measure the Headroom
Headroom is the gap between the top of the opening and the ceiling, or the lowest thing hanging down, like a pipe, beam, or light. A manual door needs about 12 inches, and an automatic opener pushes that closer to 15. If you’re tight on space, low-headroom kits exist, but leave those to a pro. Look up before you measure, since ductwork and light fixtures are the obstructions people miss most.
Step 5: Measure the Backroom
Backroom is the depth from the opening straight back to the rear wall. When the door rolls up, it needs somewhere to sit along the ceiling. Plan for the door’s height plus 18 inches, so a 7-foot door wants roughly 8.5 feet of clear depth. Add more if your opener extends further back, since the motor and rail can run several feet past the opening.
Standard Garage Door Sizes
Once you have your width and height, it helps to know what counts as normal. Here’s a quick reference for the most common residential sizes:
| Garage Type | Common Widths | Common Heights | Typically Suits |
|---|---|---|---|
| Single-Car Door | 8, 9, or 10 ft | 7 or 8 ft | One sedan, compact, or smaller SUV, plus a bit of storage room |
| Double-Car Door | 16, 18, or 20 ft | 7 or 8 ft | Two vehicles parked side by side |
| RV / Oversized | 12 or 14 ft | 10, 12, or 14 ft | Motorhomes, RVs, lifted trucks, or tall work vehicles |
Numbers that land near a standard size mean you’re likely looking at a stock door. If they don’t, you’re into custom territory, which is doable but takes longer to order and costs more.
Common Measuring Mistakes to Avoid
A handful of slip-ups cause most sizing headaches:
- Measuring the old door instead of the opening. The two aren’t the same size. Always measure the opening.
- Forgetting headroom for an opener. Enough room for the door isn’t always enough for the motor and tracks. Account for both.
- Ignoring an uneven floor. A sloped or dipped floor throws off your height and the door’s seal. Measure at several points.
- Rounding your numbers. “About 9 feet” isn’t good enough. Note the exact figure, down to the fraction.
- Measuring only once. Openings are rarely square. Take each measurement in a few spots and keep the widest and tallest.
- Skipping the obstructions overhead. Pipes, ducts, and beams eat into headroom and backroom. Measure to the lowest one, not the ceiling.
When to Have a Pro Measure Instead
Some jobs are worth handing off. Tight headroom or side room, an odd-sized opening, a space that never had a door, or simply wanting the fit guaranteed all point the same way. A wrong measurement on a custom order gets expensive fast, and a quick site visit removes the guesswork. At Joe’s Doors, we measure your opening on-site for free and confirm every number before anything gets ordered.
Frequently Asked Questions
How do I measure for a new garage door?
Measure the width and height of the opening at their widest and tallest points, then measure the side room, headroom, and backroom around it. Write down all five numbers and measure each twice. Those figures determine which door and hardware fit your garage.
What are standard garage door sizes?
Single-car doors are usually 8, 9, or 10 feet wide by 7 or 8 feet tall. The standard double door is 16 feet wide by 7 feet tall, with 18 and 20 foot options available. Custom sizes cover anything outside the norm.
How much headroom does a garage door need?
A standard door needs about 12 inches of headroom above the opening. Adding an automatic opener bumps that to around 15 inches for the motor and tracks. When space is limited, a low-headroom kit can work with far less, though it’s best installed by a pro.
Do I measure the door or the opening?
The opening, always. Your new door is sized to the opening, not to whatever door is there now. Measuring the existing door is one of the most common mistakes and often leads to the wrong size.
What if my garage floor isn’t level?
An uneven floor affects your height measurement and how well the door seals at the bottom. Measure the height at the left, center, and right, and note the differences. If the slope is significant, tell your installer so they can adjust the fit.
Can I measure for a garage door myself?
For a standard opening, yes. It’s straightforward with a tape measure and about fifteen minutes, as long as you measure carefully and double-check every number. Tight clearances or unusual framing are cases where a professional measurement is the safer bet.
Get It Measured Right the First Time
Measuring your own garage is very doable, and this guide gives you what you need to do it well. If the numbers look unusual, or you’d rather not gamble an expensive custom order on a bad measurement, that’s where we come in. Our experts at Joe’s Doors measure on-site, help you pick the right door, and handle the installation start to finish.
Call Joe’s Doors at 954-799-9787 for a free on-site measurement and estimate. We’ll confirm your new door fits perfectly before a single part is ordered.
