Measure Your Opening for a Custom Iron Door
Custom Iron Door Measuring Guide
How to measure your opening correctly for a custom pre-hung iron door.
Accurate measurements help ensure the correct fit for your custom iron door and a smooth installation, whether for residential or commercial projects anywhere in the United States.
Before You Measure
Follow these essential steps to ensure accurate measurements for your custom iron door.
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Use a tape measure and record all dimensions in inches.
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Measure the rough opening whenever possible.
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Remove interior trim for a more accurate measurement.
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Measure the width at three points and the height at two to three points.
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Record the smallest measurement if dimensions vary.
Pre-Hung Door Sizing Guide
For a typical pre-hung door, allow approximately 1 in. of additional width and ½ in. of additional height for the rough opening.
Example: Rough Opening
For a rough opening of 73 in. W × 97 in. H, a 72 in. × 96½ in. door unit may be suitable. Confirm final dimensions before production.
How IronEntryStudio Measures a Door
Our custom doors are quoted by the overall frame size (also called unit size or net frame size), not by the slab size alone.
This ensures your door is built to fit the complete pre-hung unit, including the jambs, header jamb, and threshold.
For accurate quoting, provide the complete overall size of the pre-hung unit.
Overall Frame Dimensions
Overall frame width =
Outside of the left jamb to the outside of the right jamb.
Overall frame height =
Bottom of the threshold to the top of the header jamb.
What You’ll Need
A few simple tools will help you take accurate measurements.
Tape Measure
Measure the width, height, and wall thickness.
Level
Check that the opening is level and plumb.
Notepad or Phone
Record measurements and take reference photos.
Step Ladder
Safely reach and measure taller door openings.
A Helper (Recommended)
Get assistance with measuring larger openings.
Understanding Size Types
Each measurement serves a different purpose. Here's how they compare.
Overall Frame / Unit Size
Measure the full width and height of the door unit, including the surrounding frame and threshold. This is the overall size of the complete door assembly.
Door Slab Size
Measure only the door slab itself, excluding the surrounding frame, jambs, and threshold. The slab size is always smaller than the overall unit size.
Brick Opening Size
Measure the finished masonry opening, including brick, stone, or stucco surfaces. This opening is typically larger than the overall frame size.
Net Opening vs. Overall Frame Size
Learn how door frame dimensions affect the actual usable opening.
Clear Opening Size
The clear opening is the usable space when the door is open. For example, a 36 in. frame with 2 in. jambs on each side provides approximately 32 in. of clear width.
Pivot Door Clear Opening
Pivot hardware reduces the usable opening width. For example, a 68 in. pivot door may provide approximately 48 in. of clear width, depending on its design and hardware.
How to Measure the Rough Opening
Follow these four steps to measure your door opening accurately and prepare for your new iron door.
Remove Interior Trim
Remove the interior trim, if possible, to expose the rough opening and ensure accurate measurements.
Measure the Width
Measure the opening width at the top, middle, and bottom. Record the smallest measurement to ensure an accurate fit for your door.
Measure the Height
Measure the opening height on both sides, from the subfloor to the header. Record the smallest measurement.
Check the Opening
Check that the opening is level, plumb, and square. Record any differences before ordering your door.
Rough Opening
Measure the width from stud to stud and the height from the subfloor to the header to determine the rough opening size.
How to Measure Your Custom Iron Door
Accurate jamb and arched opening measurements help ensure your custom iron door is properly sized for a precise fit and smooth installation.
Confirm Your Jamb Size
Jamb size refers to the total finished wall thickness, including drywall, sheathing, and exterior finishes. Accurate measurements help ensure a proper fit for your new iron door.
How to Measure Jamb Size
Measure from the finished interior wall surface to the finished exterior wall surface. Include all wall materials, not just the framing. Common jamb sizes include 4-9/16 in., 6 in., and 6-9/16 in. Custom sizes are also available.
How to Measure an Arched Iron Door
Arched openings require a few additional measurements beyond standard width and height. Measure the rough opening width, total height, and spring line height so we can accurately determine the arch profile for your custom iron door.
Key Measurements for an Arched Opening
Measure the rough opening width from side to side, and measure the total height from the threshold to the highest point of the arch.
Next, measure the spring line height from the threshold to the point where the straight vertical sides begin to curve into the arch.
The difference between the total height and the spring line height is the arch rise. These measurements help us determine the correct proportions and arch profile for your custom door.
If the opening is not perfectly level, plumb, or symmetrical, provide photos and measurements from multiple points so we can review the opening before production.
What We Need for an Accurate Quote
Provide a few key details about your project to help us prepare an accurate quote for your custom iron door.
Opening Dimensions
Share the rough opening width and height, along with the finished wall thickness (jamb depth). Accurate measurements help us determine the appropriate door size and frame configuration for your project.
Door Style & Configuration
Send us a photo of your preferred door style or an inspiration image. Let us know whether you need a single door, double door, pivot door, sidelights, a transom, or another configuration.
Opening Photos
Provide clear photos of your existing doorway from both the inside and outside. These help us understand the opening conditions and identify any special installation considerations.
Project Location
Share your project ZIP code so we can confirm delivery eligibility, freight access, and any location-specific delivery requirements for your custom iron door.
Avoid These Common Door Measuring Mistakes
Accurate measurements are essential for a proper fit. Avoid these common mistakes when measuring your opening for a custom iron door.
Measure the Rough Opening
Measure the actual rough opening, not the existing door or trim. Using finished door dimensions instead of the rough opening can result in an incorrect fit.
Confirm the Jamb Depth
Measure the full finished wall thickness to determine the correct jamb depth. Do not rely solely on the dimensions of the existing door frame.
Measure More Than Once
Measure the opening width and height at multiple points. Differences between measurements may indicate that the opening is not level, plumb, or square.
Check Arches & Transoms
For arched openings, measure the overall width, total height, spring line height, and arch rise. For entries with transoms, confirm the overall opening height and applicable transom dimensions.
Start Your Custom Iron Door Project
Tell us about your opening, application, style, and functional requirements.
Our U.S.-based team can help develop a custom iron door for residential or commercial use.
