Standard Garage Door Sizes — Single, Double, and RV — and How to Measure Yours Correctly

Garage doors come in more standard sizes than people expect, and ordering one takes five measurements, not one. Here are the numbers, and the traps.

Standard single-car doors

The classic single door is 8 or 9 feet wide by 7 feet tall. Nine feet has become the practical default — modern trucks and SUVs with mirrors out are wider than the cars these openings were drawn for. An 8×7 opening with a full-size pickup is a mirror-folding ritual.

Standard double-car doors

Double doors run 16 feet wide by 7 feet tall, with 15-foot widths in older tracts and 18-foot doors where three-vehicle households park two abreast. If you’re pouring a new slab, the incremental cost of 18 over 16 feet is small; the daily clearance is not.

Taller doors and RV bays

Eight-foot-tall doors are increasingly common on new construction — vans, lifted trucks, and roof boxes all thank you. Dedicated RV bays run 10 to 12 feet wide and 12 to 14 feet tall. A camper’s roof AC unit is the part people forget to measure.

The five measurements that matter

1. Opening width and height — the finished framed opening, not the old door’s panel size.
2. Sideroom — flat wall beside each jamb; vertical track needs about 3¾ inches per side.
3. Headroom — from the opening’s top to the lowest ceiling obstruction. Standard track wants 10–12 inches; low-headroom kits work in ~4½ but add cost. A ceiling-mounted opener rail needs its own clearance behind that.
4. Backroom — depth into the garage: door height plus roughly 18 inches, more with an opener.
5. The floor’s level — a sloped slab means the bottom seal needs help on one side.

What a non-standard opening really costs

Custom widths exist in 1- and 2-inch increments and cost more per door, but the expensive path is resizing the opening: reframing plus a new steel header is often four figures before the door arrives. If your opening is within an inch or two of a standard size, buy standard and let the stop molding absorb the difference.

Measure twice — the door is the one part of the house that moves every day and forgives nothing.