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Customer Guide

How to measure your door for replacement.

Four sets of measurements are all you need to order the right door the first time. Walk through them in order — it takes about ten minutes with a tape measure.

Before you start: in most cases, simply order a new door the same size as the old one. If you alter the size or add sidelights, you'll have to reframe the opening and alter many details — that usually doubles or triples the size of the job.
1

Door Size

Measure the width and height of your old door (the slab itself, not the opening).

Round up to full inches to find the size of the replacement door you'll need.

Example If your door measures 35-3/4" wide × 79-1/2" tall, you'll order a 36" × 80" door.
WIDTH HEIGHT
2

Jamb Width

Measure from the backside of the interior trim to the backside of the exterior trim.

Specify this jamb width when you order your prehung door. This guarantees the interior trim will fit flush to the wall without adding "jamb extensions."

Common sizes 4-9/16" is standard for 2×4 walls. 6-9/16" is standard for 2×6 walls. We stock both.
INT EXT JAMB WIDTH
3

Rough Opening

You'll need to remove the interior trim for accurate measurements of the rough opening.

Measure the opening width between framing members and from the bottom of the sill to the top of the opening.

Compare these measurements to the rough opening requirements of your new door to make sure it will fit.

R.O. WIDTH R.O. HT
4

Exterior Opening (or "Masonry Opening")

If you have a brick or stone door surround, this is your masonry opening.

Measure to the outsides of the exterior casing, then from the bottom of the sill to the top of the trim.

Compare these measurements with those of a prehung door that has standard 2"-wide brick molding trim. If the framed door with standard trim is too small to fill the space — or if you want a different trim style — you have three options:

  • Order a door with wider, flat casing to fit the opening The cleanest solution. You can always add decorative molding overtop to approximate your existing exterior trim style.
  • Order with standard molding and fill the gap Use additional strips of wood to bridge between the new trim and the masonry opening.
  • Order without exterior molding and make your own Best for custom or restoration work where you want to match historic profiles exactly.
MASONRY OPENING
Step 5

Got your numbers? Send them over.

We'll review your measurements and get back to you with a quote — usually same day during business hours. Prefer to talk it through? Call (904) 768-6818 or text photos.

Measurements (fill in what you have — leave the rest blank)
📸 Photos help a lot. Text pictures of your existing door, frame, and trim to (904) 238-6383 after submitting — or attach by email reply once we follow up.

By submitting, you agree to be contacted by Norwood Supply about your project. We don't share your info with anyone, ever.