How to Measure for a Storm Door
Direct Answer: To know how to measure for a storm door, measure the exterior brickmold opening width at three locations (top, middle, and bottom) and the height at three locations (left, center, and right). Record all six numbers and use the smallest width and smallest height to select your standard door size (typically 32" × 81" or 36" × 81").
3-Point Door Opening Calculator
Enter your 3 width and 3 height readings below to find your controlling opening size and matching standard door:
1. Width Measurements (Inside Trim to Inside Trim)
2. Height Measurements (Sill to Underside of Header)
✓ Fits standard openings: 35-7/8" to 36-3/8" wide by 80" to 81" high.
Where to Measure: The 3-Point Technique Explained
Door frames shift and settle over time. If a door frame is out of plumb or out of square, taking a single measurement in the center can result in a storm door that rubs or binds against the jamb.
Measure inside brickmold-to-brickmold at Top, Middle, and Bottom.
Measure from sill to underside of header at Left, Center, and Right.
Check Flat Brickmold Surface (Min 3/4" to 1")
The exterior casing (brickmold) around your door must have a flat, smooth mounting surface at least 3/4" to 1" wide. If your exterior trim is rounded or ornate, add wooden shim strips before mounting the z-bar frame.
Check Jamb Depth Clearance (Min 2-1/2")
Measure the depth of the door frame from the exterior face of the brickmold to the surface of your main interior door. You need at least 2-1/2 inches of depth so the storm door handle does not hit the handle or deadbolt of your primary door.
Standard US Storm Door Sizes Reference
| Nominal Door Size | Fits Opening Width Range | Fits Opening Height Range | Common Usage |
|---|---|---|---|
| 30" × 81" | 29-7/8" to 30-3/8" | 80" to 81" | Narrow rear or secondary side entries |
| 32" × 81" | 31-7/8" to 32-3/8" | 80" to 81" | Very common residential side/back entry |
| 34" × 81" | 33-7/8" to 34-3/8" | 80" to 81" | Older mid-century & regional front entries |
| 36" × 81" | 35-7/8" to 36-3/8" | 80" to 81" | Most common US front entry door |
| Custom Size | Outside ranges above | Special order | Historic homes or custom jambs |
Storm Door 3-Point Measurement Checklist
1. Width (Brickmold-to-Brickmold)
Horizontal2. Height (Threshold Sill to Top Jamb)
Vertical3. Essential Measuring Steps Checklist
| Door Nominal Size | Opening Width Range | Opening Height Range | Common Application |
|---|---|---|---|
| 32" × 81" | 31-7/8" to 32-3/8" | 80" to 81" | Standard side / utility entries |
| 36" × 81" | 35-7/8" to 36-3/8" | 80" to 81" | Most common front entry doors |
Common Storm Door Measuring Mistakes
Measuring the Old Storm Door Instead of the Opening
Never measure the old storm door slab. The new door includes side z-bars, an expander sweep, and hinge flanges. Always measure the brickmold opening frame itself.
Using the Largest Width Measurement
If your door top is 36.25" but the bottom is 35.75", buying a door for 36.25" will physically not fit into the bottom of the frame. Always purchase based on the smallest opening dimension.
Forgetting Handle Clearance (Doorknob Collision)
If your main entry door has a deep lever handle or deadbolt, and your jamb depth is less than 2-1/2 inches, the storm door latch will collide with your front doorknob. Check handle spacing before buying a centered-handle storm door.
Failing to Check Diagonal Squareness
Older houses settle, causing the door frame to shift out of square. If diagonal measurements from corner to opposite corner differ by more than 1/4", shimming behind the side rails may be required to keep the door from binding.
Frequently Asked Questions
How do I measure for a storm door?
Measure the width of the door opening at the top, middle and bottom, and the height at the left, center and right. Use the smallest width and smallest height. Measure inside the exterior trim (brickmould) where the new door will mount, then compare with standard sizes such as 32 by 81 or 36 by 81 inches.
What if my door opening is not square?
That is common in older homes. Always use the smallest of your three width and three height measurements, then check the sill slope and the space for the handle and hinge side before buying.
How do I measure for a storm door replacement?
Measure the opening in the exterior trim, not the old door itself. If the old storm door is still installed, you can also measure its outer frame to double-check the size, and compare with the new door's listed frame size.
How do I measure a storm door for a mobile home?
The measuring method is the same, but mobile home doors are often narrower and may swing outward, so check the opening width, the swing direction and the hinge side, and choose a door listed as suitable for it.
Do measurements change by brand or store?
The way you measure does not change. Different brands and stores list different frame sizes and required openings, so compare your smallest measurements with the exact model's size chart before buying.