Garage Door Sizing Guide: Standard Sizes, Rough Openings & How to Measure for a New Door

Why Sizing Is the First Decision, Not the Last

When homeowners call us about a new garage door, the conversation almost always starts with style and colour. That is fair. The door is the largest moving piece of architecture on the front of the house and people want it to look right. The truth, though, is that style follows size. A door that is the wrong width for your opening, or the wrong height for your vehicles, or specified without checking the headroom and sideroom inside the garage, creates problems that no amount of pretty trim can fix later.

This guide is a plain-language walk-through of how garage doors are sized in Canada, what the standard dimensions actually are, what "rough opening" means, and how a homeowner can take the right measurements before booking a quote. The numbers below come from manufacturer specifications, the Door & Access Systems Manufacturers Association (DASMA), and what we see every week in driveways across London, Strathroy, St. Thomas, and Woodstock.

The Standard Residential Garage Door Sizes

Garage doors in Canada are manufactured in a small set of widely reproduced widths and heights that fit typical garage framing. Most doors leaving a factory floor in any given week land on one of these sizes. Custom widths and heights are available, but they cost more and take longer to ship.

Single-car doors

A single-car door is anything wide enough to fit one vehicle. The vast majority of single-car garages built in Canada use one of three widths:

• 8 feet wide by 7 feet tall (8' x 7'): Common in older London homes built before the late 1980s, on narrow city lots, and in attached single garages where lot width was a constraint. Tight for a modern crossover or full-size pickup.
• 9 feet wide by 7 feet tall (9' x 7'): The most common single-door size in Canada today. Comfortable for almost any sedan, SUV, or minivan and forgiving on a slightly off-centre approach.
• 10 feet wide by 7 feet tall (10' x 7'): The choice for full-size pickups, larger SUVs, and homes where the driveway approaches the door at a slight angle. Worth the extra two feet if your daily driver is a half-ton truck.

Heights of 7 feet are standard. An 8-foot-tall single is available for taller vehicles or homes where the homeowner wants extra clearance for roof racks. Garaga, one of Canada's largest residential door manufacturers, lists single-car door widths from 4 feet up to 12 feet and heights from 6 feet to 12 feet, in custom increments. Anything outside the standard 8, 9, or 10 foot range is custom-built and priced accordingly.

Double-car doors

A double-car door is one wide door rather than two single doors side by side. The widths you will see most often are:

• 14 feet wide by 7 feet tall (14' x 7'): A "compact double" sometimes seen on older or narrower two-car garages. Tight for parking two modern SUVs side by side.
• 15 feet wide by 7 feet tall (15' x 7'): Slightly more common than 14' on infill or split-level homes from the 1970s and 1980s.
• 16 feet wide by 7 feet tall (16' x 7'): The default double in Canada and the size Garaga and most major manufacturers recommend for fitting two vehicles comfortably.
• 18 feet wide by 7 or 8 feet tall (18' x 7' or 18' x 8'): A wider double that has become more common on new builds in the past decade as vehicles have grown. Comfortable for two full-size SUVs or pickups.

An 8-foot-tall door becomes worth the upgrade once you are at 16 or 18 feet wide, especially in homes with full-size pickups, lifted suspensions, or roof-mounted bike or kayak racks. The extra foot of height also makes the door look better proportioned on a wide opening.

Oversized and RV doors

If your garage holds an RV, a tall pickup with a fifth-wheel hitch, a boat on a trailer, or a workshop vehicle on a lift, the standard residential range is too small. Manufacturers commonly produce doors up to roughly 20 feet wide and 12 feet tall for residential use. These are special-order items and they bring different opener, spring, and reinforcement requirements with them. If you are planning a garage build with a tall door, get a quote on the door before the framing crew arrives so the rough opening, the headroom, and the wall reinforcement are all sized to suit.

What Size Does Your Garage Actually Need?

The right door is the one that fits your vehicles with room to spare, fits your opening with no compromises, and matches the proportion of the home. A few rules of thumb that hold up in real driveways:

• If you drive a sedan or compact SUV, a 9 x 7 single is comfortable.
• If you drive a full-size pickup, lifted SUV, or anything with a roof rack, plan on 10 x 7 minimum, and consider 10 x 8.
• If you have a two-car garage and two daily drivers, 16 x 7 is the safe default; 16 x 8 if either vehicle is a tall pickup or SUV.
• If your driveway approaches the garage at an angle (common on corner lots and pie-shaped lots), add a foot of width over what you would otherwise pick.
• If you ever plan to store a small trailer, motorcycle, or workbench beside the parked car, build in extra width even if a smaller door would technically fit.

"Rough Opening" Versus Door Size

One of the most common points of confusion when ordering a garage door is the difference between the door size and the rough opening. They are not the same and the distinction matters when framing.

The door size is the nominal measurement of the door panels themselves, written width by height. A "9 x 7" door means the panel assembly is 9 feet wide and 7 feet tall.

The rough opening is the framed hole in the wall the door sits in. For a sectional garage door installed on a typical residential wood-framed wall, the rough opening is built to the same nominal dimensions as the door. A 9 x 7 door is installed in a 9 x 7 rough opening. The door itself mounts to the inside face of the opening on vertical wood jambs that the tracks are screwed to. This is unlike most exterior people-doors and windows, where the rough opening is sized larger than the unit to accommodate shimming and trim.

If you are building or renovating, the framer will need to know the door size so the rough opening can be built to match. Communicating the door size, not a "rough opening size," avoids ambiguity. The DASMA residential door reference materials and most manufacturer installation guides use this convention.

Headroom: How Much Space You Need Above the Door

Headroom is the vertical space left above the door, up to the lowest point of the ceiling, or to the bottom of any obstruction such as a beam, light, or HVAC duct. It is the most overlooked measurement in residential garages, and the one that most often forces a custom track configuration. The most reliable way to get it is to measure from the floor straight up to that lowest point and take the door height off the number, since an opening a couple of inches off a standard height still takes the standard door.

For a standard sectional garage door on a typical torsion spring, you need:

• About 13 inches of headroom for the horizontal track and torsion spring assembly itself.
• An additional 2 inches if you are installing a typical chain or belt drive automatic opener that runs along a centre rail.
• So a practical minimum of 15 inches of headroom for a residential door with an automatic opener.

Many manufacturers, including Garaga, recommend planning for 18 inches of headroom on new construction so the system is comfortable to service and so you have room for upgrades to insulated tracks or a different opener style.

What if you do not have 13 inches?

Tight headroom is common in older garages, in homes with finished or partially finished space above the garage, and in mid-century bungalows where the ceiling joists run low. There are real solutions:

• Low-headroom track: A double horizontal track configuration that brings the door up tighter to the ceiling. Most major manufacturers produce a low-headroom kit that needs as little as 4 3/4 inches of headroom. The trade-off is more hardware and a slightly higher cost.
• Jackshaft (wall-mount) opener: An opener that mounts on the wall beside the door rather than on the ceiling. It drives the torsion bar directly. With a jackshaft, the centre of the ceiling is left clear, which is useful in garages with cars on lifts, in heated workshops, or when ceiling space is at a premium. The opener buying guide on this site walks through the differences.
• High-lift track: For tall garages, a high-lift track lets the door travel almost vertically before tipping back to horizontal, which is useful for lift-equipped workshops or for clearing a tall vehicle. This requires more headroom than standard, not less. Our high lift calculator works out the track height, extension length, drum size and cable length for your garage.

Sideroom: Space Beside the Opening

Sideroom is the horizontal space measured from the edge of the rough opening to the nearest wall, post, or obstruction on each side. The vertical tracks and the spring system live in this space.

The minimums for a standard residential door are:

• 3.75 to 5 inches of solid framing on each side of the opening for the vertical track to be lag-bolted to. This needs to be solid wood (not just drywall on a stud).
• Slightly more for end-bearing torsion springs mounted on the side rather than at the centre.

If you are renovating a garage and the wall finish is already on, check that there is wood blocking behind the drywall the full height of the rough opening. Tracks bolted into drywall and air will not stay put.

Backroom: How Far the Door Travels Into the Garage

Backroom is the horizontal distance from the inside of the front wall (where the rough opening is) to the back wall or any obstruction. The door needs enough backroom to travel fully open along the horizontal tracks.

The rule of thumb is:

• Door height plus 18 inches for a manually operated door (so a 7-foot door needs about 8.5 feet of backroom).
• Door height plus 34 to 42 inches for a door with a standard chain or belt drive opener, because the opener carriage and rail extend past the door panels when the door is open.

A 7-foot-tall door with a standard ceiling-mounted opener needs about 10 to 10.5 feet of clear backroom. Most residential garages comfortably exceed this, but it is worth checking before you commit to a door size, especially in older garages with built-in workbenches or storage shelves on the back wall.

How to Measure Your Existing Rough Opening

If you are replacing an existing door and not doing any structural work, the simplest approach is to measure the rough opening you already have and order a door to match. You will need a tape measure, a pen, and someone to help hold the tape on a wide opening.

1. Measure the width at the bottom, middle, and top of the opening. Record the smallest of the three numbers. Older openings settle and rarely measure square. A 16-foot opening that is 192 inches at the top and 191.5 inches at the bottom should be ordered as a 16-foot door.
2. Measure the height on the left, centre, and right of the opening. Again record the smallest number.
3. Measure the headroom by standing the tape on the floor and running it straight up to the lowest obstruction above the opening. A beam, a light fixture, an HVAC duct, or a finished ceiling all count as the low point. Write that floor to lowest number down as it stands, because it is the one our checker asks for and it takes the door height off for you. That raw number is not itself the headroom: take the door height off it if you want to compare against the figures above. Measuring from the floor is the more reliable way round, since an opening a couple of inches off a standard height still takes the standard door.
4. Measure the sideroom on each side of the opening from the edge of the opening to the nearest wall, post, or window trim. Note both sides separately if they differ.
5. Measure the backroom from the inside of the front wall to the back wall, or to whatever sits closest to the door (water heater, shelving, parked vehicle).
6. Photograph the opening from inside and out. A few photos save a return trip to the garage when you are ordering parts or comparing quotes.

If any number surprises you (a side that is two inches narrower than the other, a ceiling beam dropping into the headroom, a back wall closer than expected), do not try to design around it yourself. Send the photos and measurements to your installer and let them figure out the right track configuration. We do this for free as part of any in-home quote.

With those six numbers written down, our free Will This Door Fit? checker will tell you which standard door size your opening takes, whether a standard track will work in the space you have, and what to do if it will not. It draws your own measurements back to you so you can see where the tight spot is. Nothing is saved and there is no sign-up.

Sizing for New Construction

If you are building a new garage or doing an addition, get the door sizing right before the framers arrive. A few practical points specific to Ontario construction:

• Frame the rough opening to the nominal door size. A 16 x 7 door goes in a 16 x 7 rough opening. The framer will use a header above the opening and king studs at each side; the door's vertical jambs will be applied to the inside face of the opening before the door arrives.
• Plan the headroom for an automatic opener. Ask the framer to keep at least 18 inches between the top of the rough opening and the underside of any joist, beam, or duct. Future you will be grateful.
• Double-check sideroom on attached garages. The wall between the garage and a stair, hallway, or bedroom is often where studs or HVAC chases pinch the available sideroom. A door that is too close to a side wall is awkward to install and difficult to insulate.
• Talk to the door installer about insulation values before framing. If you are putting a heated room over the garage, you will likely want a higher R-value insulated door, and that affects panel thickness and weight, which affects spring sizing. Our insulation FAQ covers the practical side of choosing R-values.
• Plan for opener power and surge protection. The opener needs a dedicated 15-amp circuit on the ceiling near the door, not a stretched extension cord from the wall.

Common Sizing Mistakes That Cost Money

After enough service calls in older London neighbourhoods, the same handful of mistakes show up again and again:

How Sizing Affects Cost

Wider and taller doors cost more, but the jump is not always linear. A few patterns that hold across most product lines:

• The price step from a 9 x 7 single to a 10 x 7 single is small. A few percent on most catalogues.
• The step from a 16 x 7 double to a 16 x 8 double is also small, often just the cost of the extra row of panels.
• Going to 18 feet wide can step the price up more noticeably because the door requires reinforcement struts across the back of each panel, heavier-gauge tracks, and a heavier-duty spring.
• Custom widths (anything outside the standard 8, 9, 10, 14, 15, 16, 18, or 20 feet) often add a custom-build surcharge and a longer lead time.
• Insulation level, window selection, and decorative hardware affect price more than width and height in most cases. We covered the trade-offs in our budget-friendly upgrades article and the windows guide.

Visualizing Your Choice Before You Buy

Once you have settled on a size, the next question is which style and colour pairs with the home. The hardest part of this decision is imagining a different door on your driveway. Two practical tools help:

1. Use a configurator. Our Build Your Door tool lets you choose width, height, panel style, colour, and window options on a representative house photo and produces an estimate.
2. Walk your neighbourhood. Look at homes built in roughly your era and note which doors look balanced. Take photos of the ones you like. Showing those photos to an installer is far more useful than a brochure description.

If you are still narrowing down style and material, our guide to garage door types and the material guide cover the trade-offs in detail. The replacement guide walks through the full decision process from sizing to install day.

When to Bring in a Professional

For straightforward replacements on a square opening with normal headroom, sizing is often something a confident homeowner can self-measure with the steps above. For anything outside the standard, an in-home assessment is worth the time. Bring us in when:

• Your headroom is under 13 inches or visibly inconsistent across the ceiling.
• The opening is not square (more than half an inch of difference between the top and bottom width measurements).
• You are converting a single-door opening to a double, or vice versa, and the framing needs to change.
• You want to add a window line or a different drive system that affects clearance.
• You are not sure whether the existing tracks are standard, low-headroom, or high-lift.
• You are building new and want to coordinate with the framer before the wall is closed in.

Our when to hire a professional article goes through how to evaluate an installer, what questions to ask, and what a good in-home quote should include.

Sizing in One Page

• The most common Canadian single-car door is 9 x 7. The most common double is 16 x 7.
• If your daily driver is a full-size pickup or you have roof racks, plan on 10 x 7 single or 16 x 8 double at a minimum.
• Door size and rough opening size are the same number for a sectional garage door. A 9 x 7 door fits a 9 x 7 rough opening.
• You need at least 13 inches of headroom for the door alone, and 15 inches with an automatic opener. Eighteen inches is the comfortable design number for new construction.
• Sideroom needs 3.75 to 5 inches of solid wood framing on each side for the tracks.
• Backroom needs to be the door height plus 34 to 42 inches to clear a standard ceiling-mounted opener.
• Not sure what your numbers add up to? The free Will This Door Fit? checker works it out for you in about a minute.
• Custom sizes are available from 4 to 20 feet wide and up to 12 feet tall, but they cost more and take longer.
• Always measure the rough opening, not the existing door, before ordering a replacement.
• Photograph the opening from inside and outside before any installer visit. The photos save time and money.
• If anything looks odd (out-of-square opening, low ceiling, unusual track configuration), get a professional measurement before ordering.