Choosing new interior doors can instantly refresh the look and functionality of your home—but only if they fit perfectly. Measuring for interior doors may sound technical, yet with the right approach, it’s a straightforward task that any homeowner can handle. Accurate measurements save time, money, and frustration when ordering from an interior doors store, ensuring a smooth installation process from start to finish.
Below is a practical, step-by-step guide to help you measure interior doors correctly and with confidence.
Why Accurate Door Measurements Matter
Interior doors are not one-size-fits-all. Even small measurement errors can result in doors that won’t close properly, scrape the floor, or leave unwanted gaps. Correct sizing ensures:
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Proper alignment and smooth operation
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Better sound insulation and privacy
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A clean, professional appearance
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Faster installation with fewer adjustments
Most interior doors store options are manufactured to standard sizes, but older homes or custom layouts often require special attention.
Tools You’ll Need Before You Start
Before measuring, gather a few basic tools:
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Tape measure (preferably metal)
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Notepad or phone for recording measurements
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Pencil
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Level (optional but helpful)
Always measure in millimetres or inches consistently to avoid confusion when ordering.
Measure the Door Width Correctly
Start by measuring the width of the door opening.
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Measure horizontally across the inside of the door frame.
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Take measurements at the top, middle, and bottom.
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Record the smallest measurement—this is the most accurate width to use.
Walls and frames can shift over time, especially in older homes, so never rely on just one measurement.
Measure the Door Height the Right Way
Next, measure the height of the opening.
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Measure from the floor to the inside top of the door frame.
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Take measurements on the left, centre, and right sides.
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Again, use the smallest measurement to ensure the new door fits without trimming issues.
If you plan to install new flooring later, factor that into your height measurement.
Don’t Forget Door Thickness
Door thickness is often overlooked but is essential for compatibility with hinges and handles.
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Standard interior doors are usually 35mm or 40mm thick.
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Measure the existing door or check hinge depth in the frame.
When visiting an interior doors store, knowing the thickness ensures your chosen door works seamlessly with your existing hardware.
Check the Door Frame (Jamb) Depth
The jamb depth is the thickness of the wall, measured from one side of the frame to the other.
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Measure from the front edge of the frame to the back edge.
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This is especially important if you’re replacing both the door and frame.
Accurate jamb depth helps avoid extra work with extensions or trims.
Identify the Door Swing Direction
Before ordering, determine whether your door is left-hand or right-hand opening.
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Stand facing the door as it opens toward you.
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If the hinges are on the left, it’s a left-hand door.
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If the hinges are on the right, it’s a right-hand door.
Many interior doors store collections allow you to choose swing direction, but only if you know it in advance.
Measuring an Existing Door vs. a New Opening
If you’re replacing an existing door, measuring the old door itself can be easier. However, if the frame is damaged or out of square, measuring the opening is more reliable.
For brand-new openings, always measure the framed opening, not the planned door size. This ensures proper clearance for fitting and finishing.
Common Measuring Mistakes to Avoid
Even small mistakes can lead to costly delays. Avoid these common errors:
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Measuring only once
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Ignoring uneven floors
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Forgetting door thickness
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Confusing frame size with door size
Taking your time and double-checking every measurement will save you from unnecessary returns or modifications.
When to Seek Expert Advice
If your home has non-standard openings, uneven walls, or you’re unsure about your measurements, professional advice can help. Many interior doors store specialists can guide you through sizing or recommend custom solutions based on your measurements.
Final Thoughts: Measure Once, Install with Ease
Measuring for new interior doors doesn’t have to be complicated. With the right tools, a careful approach, and attention to detail, you can confidently choose doors that fit beautifully and function perfectly. Accurate measurements ensure that your visit to an interior doors store results in the right door the first time—saving you effort, expense, and stress.
