Measure the finished opening at three points each way, then order using the widest width and shortest height.
Getting the right accordion door comes down to one thing: measuring the opening where it will live, not the old door you’re replacing. Grab a steel tape measure and a level, and take three width measurements and three height measurements. Use the largest width and the shortest height so the door fits the opening and clears the floor.
Measure the Opening Width
Measure the width of the finished opening at three points: the top, the middle, and the bottom. Write down all three numbers.
Use the widest of the three measurements as your width. An opening that narrows slightly toward the bottom is common, and a door sized to the widest point will still slide through the tighter spots. Record the measurement in inches — most accordion door sizes are stated that way.
Measure the Opening Height
Measure the height from the top of the opening (the header) to the floor at three points: the left side, the center, and the right side.
Use the shortest of the three measurements as your height. Floors are rarely perfectly level, and a door sized to the tallest point could drag or bind at the low spot. The shortest height accounts for that and keeps the door clearing the floor.
If the floor is visibly uneven, take three or four height measurements along the floor line and again use the shortest one.
Account for Clearance and Obstructions
Manufacturers typically deduct between 1/4 and 1/2 inch from the finished-opening height for track and floor clearance. That deduction is built into their sizing, so you don’t need to do the math yourself — just provide the raw opening measurements and let the manufacturer apply their standard clearance.
Before you order, check the opening for anything that affects fit. Look for baseboards, molding, light switches, door knobs, sill projections, or other obstructions inside the jamb. A switch plate that sticks out 1/2 inch can change how the door mounts. Note these before you measure so your numbers reflect the true available space.
Order Size and Installation Caveats
One key question to ask before ordering: does the listing ask for the opening size or the finished door size? Some manufacturers expect your raw opening measurements; others size the door to the opening with clearance already applied. Getting this backward is the most common reason a door arrives too large or too small.
Common accordion door sizes you’ll see in listings include 32 x 80, 36 x 80, 48 x 80, 48 x 96, 60 x 80, 72 x 80, and 120 x 80. If your opening falls between standard sizes, check the listing’s flexibility — some doors install in openings smaller than the stated width, though the door may not fully extend and some leaves may stay folded. Other doors cannot be trimmed at all; only the track can be cut to size. And many listings state that no returns are accepted after trimming, so double-check your numbers before you cut anything.
Once you have solid measurements, see our roundup of the best interior accordion doors to compare options that fit your opening. The sizing details from Specialty Doors’ measuring guide back up the three-point method described here.
| Measurement | Where to Measure | Which Number to Use |
|---|---|---|
| Width | Top, middle, bottom of the opening | Widest of the three |
| Height | Left, center, right of the opening | Shortest of the three |
| Uneven floor height | 3–4 points along the floor line | Shortest measurement |
If you’re measuring before the old door is removed, confirm what’s behind it. The finished opening is what matters — the old door’s frame and trim can hide the true dimensions. Take the old door down or measure the rough opening behind it, then apply the same three-point method.
FAQs
What’s the difference between opening size and finished door size?
Opening size is the raw measurement of the doorway space you’re filling. Finished door size is what the manufacturer actually ships. Most makers deduct 1/4 to 1/2 inch from the opening height for clearance, so a 36-inch opening typically takes a door that measures slightly less. Always confirm which one a listing asks for before ordering.
My opening is wider than the door’s stated size — will it work?
Yes, but the door may not fully extend across the opening. When an opening is smaller than the door’s stated width, the door still mounts, but some leaves may remain folded at the end. That leaves a visible gap. For a full extension, match the door width as closely as possible to the widest opening measurement.
Can I trim an accordion door to fit a smaller opening?
Some doors cannot be trimmed at all, and only the track can be cut to size. Others allow trimming of the door panels themselves. Many retailers also state that no returns are accepted after trimming, so verify the listing’s trim policy and your measurements before making any cuts.
References & Sources
- Specialty Doors. “How to Measure a Doorway for the Perfect Accordion Door Fit.” Details the three-point width and height method, clearance deductions, and obstruction checks.
- PCS Shutters & Doors. “Accordion Measuring Instructions.” Covers multiple height readings for uneven floors.
- Accordian Door and Wall Systems. “Measure & Install Your Accordion Door.” Confirms the finished opening as the correct measurement reference.