Open cleanly.

The door is the easy part. The three clearances are not.

Garage doors come in a short list of standard sizes, and almost every American garage takes one of four: 8x7 or 9x7 for a single, 10x8 when a pickup lives inside, 16x7 for a two-car opening. That part takes thirty seconds. What sends people back to the supplier is the space around the opening, because a door that fits the hole can still be impossible to install. Standard track needs 12 inches of headroom above the opening, 3-3/4 inches of side room on each side, and backroom equal to the door height plus 18 inches, which grows to roughly the door height plus four feet once an opener hangs from the ceiling.

The calculator above checks your opening against all of it and tells you which track style you need. This page covers the size chart, the clearances in detail, what a door actually weighs, the header span question that comes up on every new opening, and how to size an opener without paying for horsepower you cannot use.

The garage door size chart

On rough opening: for a sectional garage door, the rough framed opening is the door size. A 16x7 door goes into a 16 foot by 7 foot finished opening, and unlike a window or an entry door you do not add clearance around it. The jambs are attached inside the rough opening and the door seals against them, which is why ordering by the old panel dimension instead of the opening is the error that comes up below.

Two things about that chart. Widths step in one foot increments through the singles and two feet across the doubles, so 9x7 and 16x7 are stocked everywhere while 11x7 is a special order at a 20 to 40 percent premium and a multi-week lead time. And door height is not the same as the ceiling: the door needs its own headroom above the opening, so an 8 foot door in a garage with a 9 foot ceiling leaves exactly 12 inches, which is the standard track minimum with nothing to spare.

When you do not have the clearance

Low headroom is the most common installation surprise, and it has three fixes at three prices. A low-headroom track kit uses a double horizontal track and works down to about 4-1/2 inches, adding $100 to $250. A high-lift conversion, which raises the door higher before it turns horizontal, suits shops with tall ceilings and a car lift. And a wall-mount, or jackshaft, opener mounts beside the torsion shaft rather than on the ceiling, freeing the entire overhead area; it runs $350 to $600 versus $200 to $350 for a standard opener, and it is the right answer in any garage where storage or a lift is planned above the door.

Side room is less flexible. Below about 3-3/4 inches per side, there is nowhere to mount the vertical track, and the framing has to change. Backroom shortfalls are rarer, but a garage that is shallow front to back can leave the open door hanging over the parked car; measure from the opening straight back and confirm the door height plus 18 inches of clear ceiling before ordering, plus the opener rail if it is ceiling mounted.

Weight, springs, and why balance matters more than the opener

A two-car steel door weighs about 155 pounds bare and 210 or more insulated; a wood carriage door of the same size can pass 375. The answer people expect to that question is the opener, and it is wrong. Torsion springs carry essentially all of the weight. The opener only overcomes friction and gets the door moving, which is why a properly balanced door stays put when you lift it halfway by hand and let go. If it drops or flies up, the springs are wrong for the weight, and no opener upgrade fixes that.

This matters most on replacement. Swapping a bare steel door for an insulated one adds 50 to 60 pounds, and the existing springs were wound for the old weight. Any reputable installer re-springs with the door; if a quote does not mention springs, ask before signing. Springs are also rated in cycles: 10,000 cycles is standard, 20,000 or 25,000 cycle springs cost $50 to $150 more and roughly double the service life, which is worth it on a door opened four times a day.

How a garage door spring is specified

Spring sizing is a real calculation, and knowing the spec is useful even though the winding itself is not homeowner work. A torsion spring is described by four numbers: wire diameter, inside diameter, overall length, and wind direction. Wire diameter runs from about 0.207 to 0.283 inches on residential doors and is the number that does the most work; inside diameter is almost always 1-3/4, 2, or 2-1/4 inches; length grows with door weight and height. The pair together has to deliver enough inch-pounds per turn to lift the door weight through the drum radius, which is the actual physics under every spring chart.

Measuring an existing spring is straightforward and worth doing before you call anyone. Wire diameter: measure across 20 tightly wound coils and divide by 20, which is far more accurate than measuring one coil. Inside diameter is stamped on the stationary cone on most springs. Length is the coiled portion only, not including the cones. Wind direction matters because a door usually has one spring of each hand, and the cones are color coded, though the convention varies enough between manufacturers that it is worth confirming rather than assuming. Extension springs, the kind that run along the horizontal tracks on older doors, are simpler: they are rated by the door weight they lift, and DASMA color codes them in 10 pound steps.

The rule that turns weight into spring: the springs must balance the door, so a 210 pound insulated door needs meaningfully more spring than the 155 pound bare steel door it replaced. Cycle rating is the other lever. A standard spring is rated 10,000 cycles, which is roughly seven years at four openings a day. High-cycle springs at 25,000 cycles cost $50 to $150 more per pair and last two to three times as long, which is the better buy on any door that also serves as the main entrance to the house.

Door styles, insulation, and what they cost

Replacement cost splits into three line items that quotes often blur together: the door itself, installation labor, and the hardware that comes with it. The table below is installed cost, meaning door plus labor. Installation alone runs $200 to $500 for a straightforward single and $300 to $700 for a double, so if one quote looks far below another, check whether it includes labor, haul-away of the old door, and new springs sized to the new door's weight.

On insulation, the honest version: an uninsulated garage door is usually the largest uninsulated surface in the house, and upgrading it is the easiest single improvement to a cold garage. But the payoff depends entirely on whether the garage itself is sealed and whether it shares walls or a floor with living space. In an attached garage under a bedroom, a polyurethane door in the R-12 to R-18 range is money well spent and noticeably quieter. In a detached, uninsulated shell with gaps around the frame, an R-18 door buys very little, and the weather seal and the walls should come first. Polyurethane outperforms polystyrene at the same thickness because it is foamed in place and bonds the panel skins together, which is also why those doors feel more solid and rattle less.

The header above the opening

Every garage door opening is a hole in a load-bearing wall, and the header carries whatever the wall was carrying. IRC Table R602.7(1) gives prescriptive spans for solid-sawn headers, and the practical reading of it is this: single-door openings around 8 or 9 feet can often be spanned with doubled 2x10s or 2x12s depending on the load above and the snow load in your area, while a 16 or 18 foot double-door opening is almost always past what dimensional lumber can do and needs an engineered beam, usually LVL. That is not a detail to eyeball, and it is the one part of a garage door project where the wrong answer sags a roof rather than annoying you.

If you are replacing a door in an existing opening, the header is already there and none of this applies. If you are widening an opening, cutting a new one, or building a garage, the header size comes from the code table for your actual snow load, wall height, and what stacks above it, and any wide opening should be sized by the truss supplier, the lumberyard design desk, or an engineer. The permit will require it anyway.

Sizing the opener

Openers are rated two ways now, and the old horsepower numbers are the less useful of them. The working rules: 1/2 HP handles a standard single steel door, 3/4 HP is the right default for any 16 foot double, and 1 HP or better belongs on insulated doubles, wood doors, and any door taller than 8 feet. Newer DC openers list a force rating instead and often pair a lower nominal horsepower with more usable lifting force, so compare within a brand rather than across the label.

Drive type matters more than the horsepower number for how you experience it. Belt drives are the quiet option and the obvious choice under a bedroom. Chain drives cost $50 to $100 less and are louder. Wall-mount jackshaft units are quietest of all and free the ceiling. Every opener sold in the US since 1993 must have photo-eye entrapment protection under UL 325, and if the eyes on an existing opener are missing or misaligned, that is a safety defect to fix rather than a nuisance to bypass. Battery backup is worth the $50 to $100 in any area with outages, since a door with a dead opener and a torsion spring under load is not something to wrestle in the dark.

Where garage door projects go wrong

Measuring the door instead of the opening. Order by finished opening width and height. A 16x7 door fits a 16 by 7 foot opening; the panel itself is slightly larger and overlaps the jambs by design. Measuring the old door panel and ordering that size gets you a door too small for the hole.

Forgetting what hangs from the ceiling. Headroom is measured to the lowest thing above the opening. A light fixture, a gas line, a sprinkler head, or a garage door opener rail from a previous install all count, and installers discover them on the day.

Reusing springs on a heavier door. Covered above, and worth repeating because it is the most common way a brand new door ends up slamming shut and burning out an opener within a year.

Ignoring wind load requirements. Coastal counties and much of Florida and the Gulf require doors rated to a specific design pressure under ANSI/DASMA 108, and a standard door will fail inspection there. A garage door is the largest opening in the house and the one hurricanes exploit first; the rating is on a label on the door, and if the quote does not mention it in a rated jurisdiction, the quote is wrong.

The rest of the garage

A door replacement often travels with the rest of the bay. Framing a new or widened opening runs through the stud spacing calculator, a new or extended slab is the concrete calculator's job, and if the door upgrade is part of making the space usable year-round, the insulation calculator covers the walls and ceiling that have to come with it. The opener circuit is a wire size calculator question.

Measure the opening, then measure the three clearances, then run the calculator above. In that order, the supplier conversation takes five minutes and produces a door that actually goes in.