Door & Window Rough Opening Sizes
Standard framing rough opening width and height for common door and window sizes.
| Unit size | Rough opening width | Rough opening height |
|---|---|---|
| 2'0" (24") door | 26" | 82-1/2" |
| 2'6" (30") door | 32" | 82-1/2" |
| 2'8" (32") door | 34" | 82-1/2" |
| 3'0" (36") door | 38" | 82-1/2" |
| 36" x 36" window | 38-1/2" | 38-1/2" |
| 24" x 36" window | 26-1/2" | 38-1/2" |
| 30" x 40" window | 32-1/2" | 42-1/2" |
Why rough opening isn't the door or window size
The rough opening is the framed hole in the wall -- larger than the actual door or window unit -- that leaves room for the frame, shims, and leveling. For a standard interior door, that's typically about 2 inches wider and 2-1/2 inches taller than the door slab itself. Exterior doors and windows often need a similar or slightly larger margin, but always check the specific manufacturer's installation instructions, since rough opening requirements vary by brand and unit type.
Where these numbers come from
These are common, widely-used rough opening allowances for standard interior doors and typical window units. Manufacturer-specific rough opening requirements can differ -- always confirm the exact rough opening against the door or window unit's own installation instructions before framing, since getting this wrong means reframing.
Frequently asked questions
Is rough opening the same for every door brand?
No -- while the allowances shown here are common industry defaults, always check your specific door or window manufacturer's installation instructions, since rough opening requirements can vary by unit and brand.
What happens if my rough opening is too small?
The door or window unit won't fit without cutting into the frame, which can compromise structural support and weatherproofing -- it's much easier to shim a slightly oversized opening than to enlarge a framed one after the fact.
Does rough opening differ for exterior vs. interior doors?
Often yes -- exterior doors may need additional clearance for thresholds, flashing, and weatherproofing details, so always check the specific unit's installation requirements.
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