A storm door adds security, blocks wind and rain, and pulls natural light into a dark entryway. It only helps if it actually fits, though, so the first job is learning how to measure for a storm door before you ever load one into the car.
Get one number wrong and you end up with a heavy slab that will not sit in the opening, plus an unplanned trip back to the return counter.
This guide covers the four measurements that decide the fit, how to read a standard size chart, and the mistakes that catch most people out.
Key Takeaways
- Check for obstructions first: Look for door handles, doorbell buttons, light fixtures, railings, and porch pillars that could block the frame or stop the door from swinging open.
- Measure the height in three spots: Measure from the threshold to the underside of the top exterior trim on the left, center, and right, then use the shortest number.
- Measure the width in three spots: Measure between the inside faces of the exterior trim at the top, middle, and bottom, then use the narrowest number.
- Confirm the mounting surface: The exterior trim (brickmould) needs a flat mounting area at least 1 inch wide and 1 inch deep, set at a 90-degree angle.
How to Measure for a Storm Door
Start by checking for obstructions. Pillars, mailboxes, and overgrown foliage can all stop a door from swinging open fully, and even the thickness of your house numbers or a bulky doorbell can crowd the frame during installation.
Next, decide the handing of the door, which just means the side the hinges sit on. In most cases you want the storm door to hinge on the same side as your main entry door, so the two swing open together. If an obstruction blocks that side, move the hinges to the other side instead.
Take a close look at your main entry door handle too. A large decorative handle set can strike the glass or screen of the storm door when either one opens. You may need to extend the storm door frame outward with a spacer, or choose a handle with a lower profile.
Here is an at-a-glance list of common obstructions to watch for:
- Door handles (measure how far they stick out).
- Pillars or columns.
- Porch railings.
- Mailboxes.
- Plants or bushes.
- House numbers.
- Doorbells.
- Outdoor light fixtures.
One To Watch
Always choose the hinge side with the fewest obstacles so the door can swing open fully.
What You’ll Need
- Tape measure.
- Pencil.
- Notepad or paper.
1. Measure the Height
Measure the height of the opening from the top of the metal threshold (the plate you step over) up to the underside of the header, which is the top piece of exterior trim.
Do this three times: once on the left, once in the middle, and once on the right. Ideally the numbers match. If they do not, use the shortest measurement as your guide, since few openings are perfectly square and the door has to clear the tightest point. Most standard storm doors fit openings between 80 and 81 inches high. Write the number down right away.
2. Measure the Width
Measure the width of the opening between the inside faces of the exterior trim (often called the brickmould), from the left side across to the right.
Measure at the top, middle, and bottom of the frame. As with the height, use the narrowest width as your guide. Width is the number people get wrong most often, so measure the opening itself, never the old door slab, which always sits smaller than the space around it.
3. Check the Mounting Surface Depth
Most storm doors mount directly onto the face of the exterior trim (brickmould), so you need enough flat surface to attach the mounting rails.
Measure the width of the face of your trim. As a rule, you need a flat mounting area at least 1 inch wide and 1 inch deep, set at a 90-degree angle (1). If your trim is decorative, curved, or too narrow, plan to add a mounting strip or shims to build a flat surface. Hinge-side shims are often needed to square up an out-of-true opening, and they do not come in the box, so a paint stir stick or a wooden yardstick works in a pinch.
4. Estimate the Size
Door sizes are always written as Width x Height. Pair your narrowest width with your shortest height to land on a size.
For example, a 36-inch width and an 80-inch height points you to a 36×80 storm door. If your numbers fall slightly outside the standard ranges, most installation kits include adjustment rails (Z-bars) that absorb the small gaps.
Top Tip
Measure twice, buy once. One wrong number on the notepad turns into a heavy return and a wasted afternoon.
Standard Storm Door Size Chart
Manufacturers lean on standard sizes because they are cheaper to mass-produce. If your home was built in the last 30 to 40 years, the odds are in your favor.
Your opening will probably fall between 30 and 36 inches wide and 80 to 81 inches high. Most standard doors come 32 or 36 inches wide, and some brands add 30 and 34-inch options. If your measurements line up with the chart below, you can grab a door off the shelf at most home improvement stores. A custom size usually means a higher price tag.
The chart below lists standard door fit ranges from major brands like Andersen, EMCO, and Larson.
| Standard Size Width Range | 30 inches | 32 inches | 34 inches | 36 inches | Standard Door Height Range |
| Andersen 3000 and 4000 storm door (Easy Install System) | 29.88 to 30.38 inches | 31.88 to 32.38 inches | 33.88 to 34.38 inches | 35.88 to 36.38 inches | 80 to 80.88 inches |
| Andersen 3000 TruEase, 2500, and 200 series (excluding Forever®) | 29.75 to 30.38 inches | 31.75 to 32.38 inches | 33.75 to 34.38 inches | 35.75 to 36.38 inches | 80 to 80.88 inches |
| Larson (No Shim Required) | 29.88 to 30 inches | 31.88 to 32 inches | 33.88 to 34 inches | 35.88 to 36 inches | 80 to 81 inches |
| Larson (Shim Required) | 30.88 to 31.17 inches | 32.17 to 32.88 inches | 34.17 to 34.88 inches | 36.17 to 36.88 inches | 74.5 to 75.5 inches |
Note that a “36-inch door” isn’t exactly 36 inches wide; it is built to fit an opening of roughly 36 inches, and the adjustment rails fill whatever gap is left.
Custom Size Storm Doors
Sometimes standard just does not work. If you live in an older historic home with unusually tall doors, or a mobile home with a narrow 30 or 32-inch entry, you may need a custom order.
Most major hardware stores can order custom sizes from manufacturers like Larson or Andersen. You will need to hand the associate your exact measurements, and you should expect a lead time of several weeks and a higher price point.
FAQs
Brewing Up a Storm
Getting the measurements right is most of the job with a storm door. Once your height, width, and mounting depth are confirmed and written down, choosing the actual door is the easy part.
Whether you grab a standard model off the shelf or order a custom size for an unusual entryway, accurate numbers are what make the install go smoothly. Spend the extra few minutes with the tape measure now, and you can skip the return line later.
