Technical Free

Door/Window Rough Opening Calculator

Enter finished door or window size, get required rough opening dimensions. Supports interior, exterior, drywall, and masonry frames.

Rough Opening Dimensions

RO Width
--
RO Height
--
Width Added
--
Height Added
--

Always verify local building codes. Some jurisdictions require additional tolerances.

📊

Save this calculation to your account

Create a free account to save your results, compare sizing options side by side, and download a branded PDF you can attach to a quote.

Email these results to yourself

Get a copy you can reference on the job site or attach to a quote.

How to Use This Calculator

1. Select door or window. Doors and windows have different tolerance requirements.

2. Choose interior or exterior. Exterior openings need slightly more tolerance for weatherstripping and flashing.

3. Enter the finished unit size. This is the door slab or window unit size, not the frame size.

4. Select frame type. Masonry openings require extra tolerance compared to standard drywall/wood stud construction.

Frequently Asked Questions

What is a rough opening for a door?
A rough opening is the framed opening in the wall that holds a door or window. For interior doors, the rough opening is typically 2 inches wider and 2.5 inches taller than the door slab.
How much bigger should a rough opening be?
For interior doors with drywall frames, add 2 inches to width and 2.5 inches to height. For exterior doors, add 2.5 inches to width and 2.25 inches to height.
What is the rough opening for a standard 36 inch door?
A standard 36 inch interior door needs a rough opening of 38 inches wide by 82.5 inches tall (assuming an 80 inch door height).
What is the rough opening for a window?
For standard replacement windows in drywall frames, add 0.5 inches to both width and height. For exterior windows, add 1 inch to both dimensions.

Related Handyman Tools

Technical

Shelf Load

Calculate safe weight capacity for any shelf setup.

 Technical

Drywall Patch

Estimate drywall patch cost with materials, labor, and markup.

 Technical

Caulk Coverage

Calculate cartridges needed for any caulking job.

 Technical

Tile & Grout

Calculate tile count, grout amount, and cost for any job.
← View all Handyman tools