Interior

TL;DR: When installing a new door, knowing how to measure the rough opening is essential. The rough opening is the framed space in a wall where a door will be installed—it’s larger than the door itself to allow room for the frame, shims, and insulation. Accurate measurements help ensure a proper fit, smooth installation, and professional results. Measure width, height, and wall depth carefully before selecting your door.

Need help choosing or customizing a door? Call 866-739-1636 or contact us online to speak with a team member or visit your local Builders Surplus.

When you’re ready to purchase a new door, you’ll need to have an idea of what size door you’ll need. Therefore, measuring rough openings for doors prior to purchasing is an important step in your home remodeling.

Also, do you want a pre-hung door? This is where the door jamb (or frame) is already attached to the door. The opening in your home is there and the door is ready to be installed in it. Or do you need a slab door? This is an unmounted single door only (no jamb attached) which is used to replace a door if the frame is already in place. As a result, you’ll need to apply hinges to mount this door to the frame.

Pre-hung doors (left); Slab doors (right)

Doors: Measuring Rough Openings

We’ve included two charts showing approximate openings for doors. The first is for exterior doors and the second chart is for interior doors. Also, if you’re planning on doing it yourself, these rough measurements should help to make the installation a bit easier.

Standard Sizes

Door widths which are considered standard usually come in sizes of 2/6 (30”), 2/8 (32”) and 3/0 (36”). Standard door heights are 6/6 (78”) and 6/8 (80”). In addition, special sizes can sometimes be custom ordered. A 36” x 80” pre-hung single door will use a rough opening of approximately 38-1/2” x 82-1/4” to fit. Always remember to square up your door before you nail the frame in place to assure it will close properly.

Not sure if your measurement is accurate? You can always visit your favorite Builders Surplus location to speak with one of our associates. We’ll do our best to answer any questions you have regarding doors and measuring rough openings.

REACH OUT TO SEE WHICH DOOR STYLES BUILDERS SURPLUS HAS AVAILABLE AT YOUR LOCAL STORE!

FAQs: Measuring Doors and Rough Openings

Q: What is a rough opening for a door?
A: It’s the framed opening in the wall—slightly larger than the actual door—to allow room for the jamb, shims, and adjustments during installation.

Q: How much bigger should the rough opening be than the door?
A: Typically, the rough opening should be about 2 inches wider and taller than the door size (e.g., a 36″ x 80″ door needs a 38″ x 82″ rough opening).

Q: What should I measure when replacing a door?
A: Measure the width, height, and wall depth of the rough opening. Always double-check at multiple points to ensure it’s level and square.

Q: What tools do I need to measure a rough opening?
A: You’ll need a tape measure, level, and possibly a framing square to check for squareness.

Q: Can I install a door myself?
A: Many DIYers can install prehung doors with proper measurements and instructions. If you’re unsure, our team is happy to help or refer a pro.

Q: What if I need a custom-sized door?
A: No problem! Builders Surplus has an on-site Custom Door Shop for special orders, unique sizes, and modifications.