Have you ever attempted to replace your door knobs or handles only to find that the new hardware doesn’t fit properly? If so, you’re not alone. This frustrating experience is often the result of inaccurate measurements.
Accurate door hardware measurements are essential for a seamless installation and functional operation. Incorrect measurements can lead to a variety of issues, including, incompatible hardware, protruding hardware, or damaged door.
I learned the hard way: when I was a beginner DIYer, I eyeballed the measurements only to end up with a loosely rattling knob that didn’t fully latch. I had to remove the set and refill multiple new screw holes.
Don’t make my mistake! Let’s see how to properly measure for new door hardware.
When you want to install a new door knob or handle, you basically need to measure three things:
- the backset
- the diameter of the bore holes (edge bore and cross bore)
- the thickness of the door
First, take a close look at this diagram, it shows every part of the door that you need to know to do proper measurements:
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How to Measure the Backset
The backset refers to the horizontal distance from the edge of the door to the center of the knob or handle.
Standard interior doors usually have either a 2-3/8″ or 2-3/4″ backset. This measurement must be matched precisely by your new hardware for proper installation and functionality.
To determine your existing door’s backset:
- Remove the current door knob and use a tape measure to measure horizontally from the door edge to the center screw of the knob.
- You can also measure vertically from the midline of the knob/handle to the edge of the door.
- Ensure your new hardware matches this backset measurement exactly.
Getting this measurement accurate is crucial – an even slightly off center knob/handle will lead to scraping on trim, latching issues, and other problems.
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How to Measure the Bore Hole and the Edge Bore
The bore hole, also known as the cross bore, is the large hole where the door knob or handle goes through. The standard diameter for most interior doors is 2 1/8″.
The edge bore, also known as the latch bore, is the small hole on the edge of the door where the latch or the bolt goes through. The standard diameter is usually 1″.
If the bore hole or the edge bore are too small, the door knob or handle will not fit. If the bore hole or the edge bore are too large, the door knob will be loose and wobbly.
To measure the bore hole and the edge bore, you will need a tape measure or a ruler.
Here are the steps to follow:
- Remove the existing door knob or handle from the door. You may need a screwdriver or a hex key to do this, depending on the type of door knob or handle you have.
- Place the tape measure or the ruler across the bore hole (in the middle). Make sure the tape measure or the ruler is straight and level.
- Read the measurement from the tape measure or the ruler. This is the diameter of the bore hole.
- Place the tape measure or the ruler across the edge bore.
- Read the measurement from the tape measure or the ruler. This is the diameter of the edge bore.
How to Measure the Thickness of the Door
Your new hardware must be compatible with the door’s thickness to ensure a secure fit.
Here are the steps to follow:
- Open the door and place the tape measure or the ruler on the edge of the door. Make sure the tape measure or the ruler is perpendicular to the door.
- Read the measurement from the tape measure or the ruler. This is the thickness of the door.
The thickness of the door is usually between 1 3/8 inches to 1 3/4 inches for standard interior doors, and between 1 3/4 inches to 2 inches for standard exterior doors (source).
However, some doors may have different thickness, especially if they are custom-made or have been modified. Therefore, it’s always best to measure your own door to be sure.
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Additional Measurements to Consider
Faceplates: Square vs. Round Edges
Faceplates are part of the latch assembly and they allow you to attach the latch to the edge of the door (typically with two screws). They come in two main styles: square-edged and round-edged.
When selecting new door hardware, choose faceplates that match the old faceplate. If your existing door has a square-edged faceplate, you should choose new hardware with a square-edged faceplate to avoid extra work. Conversely, if your existing door has a round-edged faceplate, you should choose new hardware with a round-edged faceplate.
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