Interior & Exterior Doors
Getting accurate measurements is the most important step before ordering a new door. A door that’s off by even a quarter inch can cause installation delays, gaps, or drafts. Follow this guide to measure your door opening correctly.
Tools You’ll Need
- Tape measure (steel, not cloth)
- Pencil and paper
- Level
- A helper (recommended for exterior doors)
Step 1: Measure the Width
Measure the width of the door opening (not the existing door) in three places:
- Top of the opening, jamb to jamb
- Middle of the opening
- Bottom of the opening
Use the smallest of the three measurements as your width. Openings are rarely perfectly square, especially in older homes.
Step 2: Measure the Height
Measure the height of the opening in three places:
- Left side, from the head jamb to the floor
- Center
- Right side, from the head jamb to the floor
Again, use the smallest measurement.
Step 3: Measure the Jamb Depth (Wall Thickness)
Measure from the outer edge of the exterior trim to the outer edge of the interior trim, or simply the thickness of the wall at the opening. Standard depths are:
- Interior doors: 4 9/16″ (for 2×4 walls) or 6 9/16″ (for 2×6 walls)
- Exterior doors: 4 9/16″ to 6 9/16″ depending on wall construction and insulation
Step 4: Check for Square
Use a level to check that the jambs are plumb (vertical) and the head jamb is level. Measure both diagonals of the opening corner to corner — if the two diagonal measurements match, the opening is square. A difference of more than 1/4″ means the opening is out of square and may need adjustment during installation.
Step 5: Note the Swing Direction
Stand outside the door (exterior) or in the hallway (interior) facing the door as it would open toward you:
- Left-hand (LH): Hinges are on your left, door opens toward you
- Right-hand (RH): Hinges are on your right, door opens toward you
For exterior doors, always determine handing from outside the home looking in.
Interior Door Standard Sizes
| Width | Height | Common Use |
|---|---|---|
| 24″–28″ | 80″ | Closets, small rooms |
| 30″–32″ | 80″ | Bedrooms, bathrooms |
| 36″ | 80″ | Main hallway/entry doors |
Exterior Door Standard Sizes
| Width | Height | Common Use |
|---|---|---|
| 32″ | 80″ | Side/service entry |
| 36″ | 80″ | Standard front entry |
| 72″ (double) | 80″ | Double front entry |
Additional Measurements for Exterior Doors
- Threshold width: Measure the full width of the sill area
- Sidelights/transoms: If your door includes sidelights or a transom window, measure each separately
- Exterior clearance: Note any obstructions like porch railings, storm doors, or steps that could affect installation or door swing
Pro Tips
- Always measure the rough opening, not the old door itself — old doors may have been trimmed or shimmed.
- Measure twice, order once. Small errors are far more costly to fix after a door has been ordered or cut.
- If any measurement seems unusual or the opening is significantly out of square, consult a professional installer before ordering.
- When in doubt about jamb depth, measure your wall thickness directly with a tape measure through an outlet or vent opening.
Still unsure about your measurements? Contact our team — we’re happy to walk you through it or schedule an in-home measurement.
