How to Measure for your New Garage Door? (Detailed GUIDE)

Saad Iqbal | 🗓️Modified: October 26, 2023 | ⏳Time to read:15 min

When it comes to installing a garage door, it’s not as straightforward as just measuring the width and height of the opening.

To guarantee a perfect fit for the springs, track, hardware, and garage door opener, you need to consider a few more crucial measurements.

Garage door measurement include:

  • Headroom Clearance
  • Sideroom
  • Backroom

You need to make sure the measurements are accurate as it can make or break your entire project.

Overlooking these specifics can lead to frustrating delays and unexpected expenses. In this guide, we’ll walk you through the art of measuring for a garage door, helping you get it right the first time.

Table of Contents

What’s the Ideal Size for Your Rough Opening?

As a general guideline, the rough opening should match the exact dimensions of the door you intend to install.

Measuring to install a new door

For instance, if you’re eyeing a standard single-car door measuring 9ft in width by 7ft in height, your rough opening should mirror those dimensions.

The width always comes before the height when sizing up garage doors. So, when you see 9×7, it means a door that spans 9 feet in width and 7 feet in height.

Some builders prefer to slightly reduce the width of the rough opening to 8’10” or 8’11” for a 9ft wide door, ensuring that the metal door end stiles rest snugly against the door jambs.

this practice isn’t mandatory, it’s favored for its advantages, such as minimizing rattling during windy weather and offering a more robust seal in snowy climates. It also keeps unpainted metallic end stiles out of view when there’s no perimeter seal in place.

Measure for door replacement

But here’s an important tip: while you can be a bit flexible with the door width, the door’s height is typically framed to match the exact rough opening height. This is vital to ensure everything aligns correctly.

Chances are the people who initially constructed your rough opening did a good job maintaining level and square dimensions.

However, if you’re repurposing an existing opening, or if you’re just extra cautious, consider taking multiple width and height measurements from offset positions.

This way, you can detect any unusual dips or slopes in the concrete or header. This is particularly crucial for taller doors, especially on older buildings.

Now, if you’re measuring for the replacement of an existing garage door, you’ll need to size up both the rough opening and the current garage door panel configuration.

Here’s a quick tip: a typical 7ft tall garage door consists of four 21″ sections, while an 8ft garage door comprises two 21″ sections and three 18″ sections.

For some special doors like carriage house or commercial doors, you’ll find four 24″ sections.

It’s vital to match the existing panel configuration, especially when you’re dealing with multiple doors installed side by side.

Consistency is key!

Choosing the Right Garage Door Design

Selecting the ideal garage door size is contingent upon the dimensions and design of your garage space.

The design blueprints for garages can vary considerably, ranging from compact structures intended for a single vehicle to more spacious layouts accommodating standard two-car garage doors or even multiple vehicles.

If you’ve purchased an existing home, the choice of garage door size may already be predetermined for you. However, for those building new homes or renovating, various essential factors come into play:

  • Personal Preferences and Vehicle Count: Your personal preferences, style, and the number of vehicles you own are pivotal determinants when deciding on the size of your garage door. A single or multiple-car garage door will be chosen based on your needs.
  • Aesthetics and Home Facade: The appearance and aesthetics of your home’s garage facade are significant considerations. The garage door design should complement and enhance the overall look of your house. It’s not just about functionality but also about how it impacts your home’s curb appeal.
  • Practicality and Cost Considerations: Practicality plays a crucial role in the decision-making process. Installing multiple doors and an opener system may come with maintenance and cost implications. Assess the practicality of maintaining and operating multiple garage doors and consider the associated expenses when making your choice.

Different sizes for different uses

Single Car Garage Door Dimensions

For those with smaller garage spaces intended for just one vehicle, single garage doors are the perfect choice.

These doors are typically available in two common dimensions: 7 or 8 feet in height and 8, 9, or 10 feet in width. Single car garage doors are designed to accommodate a single standard-sized car, SUV, truck, or van.

Double Car Garage Door Dimensions

Homes equipped with multi-vehicle garages usually opt for double garage doors. These doors come in heights of 7 or 8 feet and widths of 16 or 18 feet.

They are particularly popular among homeowners who plan to use a section of their garage for activities like workshops or storage.

RV Garage Door Dimensions

For individuals with specialized needs, such as the need to park multiple vehicles or store an RV, larger garage doors are available. These oversized garage doors typically have dimensions of 10, 12, or 14 feet in both height and width, providing ample space for accommodating larger vehicles.

Combination Garage Doors

As depicted in the graphic above, many garages adopt a combination approach, utilizing either multiple single doors or a combination of single and double doors.

These designs offer increased space and flexibility but come with the requirement for maintaining and managing at least two separate openers and garage door systems.

While offering versatility, it’s essential to consider the upkeep and maintenance of these combined garage door systems, including multiple openers and associated mechanisms.

Dealing with Uneven or Non-Square Measurements

Uneven floors with dips, crowns, or slopes are a common challenge.

But the good news is that garage doors aren’t designed to mirror these floor slopes. Instead, the bottom retainer and seal can be adjusted to cope with such variations.

Adjustable aluminum extrusions with 3″ side walls are shaped like the letter “U.”

They are used over the bottom section of the door to conform to the floor’s slope. A slightly wider bottom weatherstrip is then added to enhance the seal.

Additionally, all garage doors should have perimeter weather seals known as vinyl door stops.

These seals are attached to both door jambs and the header to seal the door and hide any gaps. They are secured in place with matching color trim nails, spaced 18 inches apart.

Preparing Space for Your Garage Door Opener

If you’re planning to install a garage door opener with drawbar operation, keep in mind that it typically requires about 2.5″ of space above the door.

This added space requirement needs to be factored in, especially if there isn’t much room available above the door.

For existing doors, you should account for approximately 3″ of extra headroom to accommodate the rail and mounting bracket above the torsion spring shaft.

In the case of sidemount jackshaft openers, the space requirement is similar to standard openers. The casing for the opener is positioned above the torsion spring line, demanding about 4 inches of space above the torsion shaft.

Step 1: Measuring the Width

When measuring the width, gauge the finished opening at its widest point.

  • Take measurements from both ground level and eye level to address any non-square aspects of the frame.

You’re essentially measuring how wide the door should be, spanning from one side of the opening to the other. For safety and durability, residential doors are typically framed with 2″ x 6″ wood.

Keep an eye out for openings that are not square and for any signs of weakened or rotting boards. Never install a garage door on an unsafe or unsound door frame.

Step 2: Measuring the Height

  • Measuring the height involves determining the highest point of the finished opening while also considering any irregularities in the floor and header.

 In cases where the concrete floor hasn’t been poured yet, you’ll need to consult with the builder to determine the thickness of the finished floor and then subtract that from your measurement.

Step 3: Decoding Headroom

  • For residential garage doors, a general rule of thumb is to have a minimum of 18″ of headroom.
  • However, if you’re dealing with an exceptionally large commercial-sized door, 24″ of headroom is ideal.

Having this space ensures that almost any type of opener, hardware, and track combination can be installed. While you can get away with less headroom, it significantly limits your door configuration options.

One key detail many people overlook is that headroom isn’t solely the measurement from the header to the ceiling.

It should be measured from the header to the nearest obstruction. You might have a generous 3 feet of space above the door, but if there’s a pipe or ductwork positioned just 10″ above the header within the door’s path, you have a problem.

In such cases, you’ll either have to use high lift tracks to go over the obstruction or frame down the opening to go under it.

Measuring headroom for residential doors is relatively simple, as they are usually less than 9 feet in height.

A standard tape measure will help you identify obvious obstructions.

For taller doors or larger commercial-sized openings lacking proper lighting, a laser tape measure can be a handy tool.

Step 4: Sideroom Exploration

The vertical tracks within the garage opening require adequate space for the “L” shaped brackets to securely attach to the door jambs.

For standard residential tracks, they are typically installed with the brackets extending outward toward the exterior wall, secured with lag bolts.

On both sides of the garage door, a minimum of 4 inches of side room is needed for a standard 2″ vertical track.

If you’re dealing with commercial doors and standard lift systems, you’ll require about 6 inches of space.

Sideroom measurements are taken from the door jamb to the nearest obstruction, which is usually a wall.

Besides accommodating the track brackets, you also need to allocate space for the tube or shaft holding the torsion springs.

On a 16-foot-wide garage door, the typical shaft or tube measures around 16’10”. While you can trim the tube on each side, the minimum required space is about 16’8″.

Standard drawbar openers with a rail and J-arm system usually fit within the width of the door.

However, sidemounted openers have distinct sideroom requirements. For instance, the Liftmaster 8500 jackshaft opener’s motor and casing need about 8 inches of space to the nearest obstruction, usually the sidewall.

Step 5: Navigating Backroom Space (Depth)

Backroom, often referred to as depth, is the measurement from the header to the nearest obstruction behind the path of the door while it’s overhead.

This space is critical for ensuring that the door, opener, and horizontal tracks have enough room for proper installation.

Insights on Rollup Door Measurements

Unlike sectional garage doors that are linked together with hinges, rollup doors roll into a barrel and mount over the header.

The diameter of the barrel is directly proportional to the door’s height, gauge, and insulation inside the curtain. Measuring the height and width of a rollup door follows a similar process to sectional doors, but there are distinct requirements for headroom and sideroom.

Rollup Door Rough Opening

To measure a rollup door’s rough opening, you need to gauge the height and width of the opening at its highest and widest points.

Keep an eye out for irregularities such as non-square jambs.

Unlike sectional doors, which can span up to 30 feet in width, rollup (sheet) doors generally top out around 20-foot widths.

If you’re eyeing a wider barrel-style door, you might need to consider a rolling steel door instead of a sheet (rollup) door. Rolling steel doors are built to be robust and strong, thanks to their interlocking slats as opposed to one continuous sheet.

Rollup Door Headroom: The Vertical Challenge

If you plan to install a rollup door but aren’t sure about the specific model or features you want, it’s a wise move to allocate a generous 24 inches of headroom.

The minimum headroom space for barrel-style doors depends on the curtain’s thickness and the door’s height.

Taller openings require more headroom because, as the door rolls up, the barrel’s diameter increases. The same principle applies to insulated rollup doors and doors with heavier gauge steel.

Entry-level mini storage models like the m650 typically need only 18″ of headroom, while the model 2500, constructed with 26-gauge steel, requires 23″ of headroom. If you intend to add a hood cover or insulation, you should account for an additional 2 inches of space.

Rollup Door Sideroom: A Side Story

Sideroom requirements for rollup doors differ from those of sectional doors. You’ll need at least 9 inches of space on each side of the rollup door.

If you’re planning to add a side-mounted opener, you’ll require a minimum of 24 inches of room on at least one side. The exact sideroom necessary for an opener will depend on the model you’re installing.

Pro Tips for Measuring

When it comes to measuring, here are some important considerations to keep in mind:

  • If you’re measuring an area with an unfinished floor, collaborate with the contractor or homeowner to determine the height of the poured concrete. If you must install the garage door before the flooring is complete, you may need to adjust your vertical track to compensate. Additionally, always account for unlevel flooring, low spots in the concrete, and potential water leakage into the garage.
  • Ensure there’s an electrical outlet within reach for an automatic opener. Most electric openers come with a 4-foot power cord, so relying on an extension cord isn’t recommended.
  • Examine all the woodwork in your garage to confirm its structural integrity. Look out for split, warped, or rotten boards. When working on woodwork, ensure it’s done using 2″ x 6″ boards.
  • Make sure the vertical bucking extends 24 inches beyond the door’s height. End bearing plates must be fastened at the spring line level.
  • Provide a spring pad for the center bearing plate and spring line to anchor into. This pad is typically mounted in the headroom space at the center of the garage.
  • Keep an eye out for any obstructions like ductwork, pipes, and electrical cords that might obstruct your garage door installation.

Remember that garage doors come in various sizes, with common dimensions being 8×7, 9×7, and 16×7. However, it’s crucial not to assume that a door is a standard size; always measure each door to ensure a precise fit.

The bottom line

When it comes to garage door installation and measurements, precision is the name of the game. These details might seem technical, but they play a crucial role in ensuring that your garage door fits perfectly, operates smoothly, and stands the test of time.

Whether you’re setting up a new door or replacing an existing one, following these guidelines will save you time, effort, and potentially costly adjustments down the road.

And remember, safety always comes first! So, when in doubt, seek the advice of a professional and take all necessary precautions.

Happy measuring and good luck with your garage door project!

Reviewed and Verified by

The article has been duly reviewed by the industry experts and garage door business owners. Here’re the experts that have verified the information in the article:

Continental Door Company – They’re dealing in residential and commercial garage door work for customers in Spokane, Spokane Valley, Coeur d’Alene, and the surrounding areas.

Beanstalk Builds – Beanstalk builds helps you discover the “jack of all trades” inside yourself. On this channel theydemonstrate how to’s, tips, skills, and techniques from all facets of life with a primary focus on encouraging viewers to do it themselves all while doing it safely of course!

Door to Door Design – Door to Door garage doors is the primer garage door company servicing Northern New Jersey for residential garage doors and electric openers. Our channel will show case tips and tricks for your garage door.

Saad Iqbal is a professional civil engineering and freelance write. He's passionate about structures, construction management, and home improvement topics. He's been working as a Senior Engineer in a consultant firm for over 8 years. Besides he loves writing informative and in-depth content focused on construction and home-related topics. You can catch him at his linkedin page or reach out via our contact us page.

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6 thoughts on “How to Measure for your New Garage Door? (Detailed GUIDE)”

    • Hi there, thanks for asking;

      A standard 2 1/2 car garage typically has a garage door opening that is approximately 16 feet wide and 7 feet high. This allows enough space for two cars to park side by side and some additional space for storage or maneuvering.
      The exact dimensions may also depend on the design and layout of your garage, so consult with a professional if you have specific requirements or constraints.

  1. I’m rebuilding a garage that was a three car. I’ve converted it to a two car garage. Trying to figure out what size doors I need.

    • When converting a three-car garage into a two-car garage, you’ll need to determine the appropriate garage door size to accommodate two cars. Standard two-car garage doors typically come in the following standard sizes:

      Single Door: A single door for a two-car garage is typically 16 feet wide and 7 to 8 feet high. This allows enough space for one car to enter and exit the garage.

      Double Door: If you prefer a double door design for your two-car garage, you can use two single doors side by side, each measuring 8 feet wide and 7 to 8 feet high. This provides separate openings for each car.

    • For a standard 16-foot wide garage door that is either 7 feet or 8 feet high, the rough opening typically needs to be slightly larger than the door’s actual dimensions to allow for proper installation and operation. The typical rough opening sizes for such garage doors are as follows:

      For a 16′ wide x 7′ high garage door: The rough opening should be about 16 feet wide by 7 feet 2 inches to 7 feet 3 inches high.

      For a 16′ wide x 8′ high garage door: The rough opening should be about 16 feet wide by 8 feet 2 inches to 8 feet 3 inches high.


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