Four measurements. Two minutes. Zero surprises when the hardware arrives. Here's the exact process.
Four measurements. Two minutes. That is all it takes to confirm that any lever, knob, deadbolt, or entry set will fit your door before you order. These measurements eliminate the most common pre-purchase mistakes and make the installation process straightforward. Here is exactly how to take them.
Measurement 1: Backset
The backset is the horizontal distance from the flat edge of the door — the side where the latch slides out — to the centre of the large round bore hole where the lever or knob mechanism sits.
How to measure: open the door, look at the existing latch, and measure from the door edge to the centre of the latch hole. If you are measuring an existing lever or knob, the centre of the spindle hole is the reference point.
- 2-3/8" — standard for most interior doors
- 2-3/4" — standard for exterior doors and deadbolts
If you do not have an existing door prepped, check with your millworker — most standard pre-bored interior doors come at 2-3/8". See our full backset guide: What Is a Backset?
Measurement 2: Bore hole diameter
The bore hole is the large round hole drilled through the face of the door for the lever or knob mechanism. The standard diameter in North America is 2-1/8" (54 mm). Almost all residential hardware is designed for this size.
Occasionally — particularly in older homes or imported doors — the bore hole is a different diameter: 1-1/2", 2", or metric equivalents. If your bore hole is non-standard, you may need an adapter rose or a hardware set specifically designed for that size. Always measure the diameter before assuming it is standard.
Measurement 3: Cross-bore (latch bore) diameter and depth
The cross-bore is the smaller hole drilled into the edge of the door where the latch mechanism sits. The standard diameter is 1" (25 mm). This is consistent across virtually all residential hardware in North America. The depth of the cross-bore (how far into the door edge it goes) needs to accommodate the latch body — typically 2-3/8" to 2-3/4" deep, which corresponds to the backset.
When replacing hardware, confirm the cross-bore diameter matches the latch faceplate on your new hardware. A latch faceplate that is too wide will not sit flush in an undersized cross-bore without enlarging the mortise.
Measurement 4: Door thickness
Most lever and knob sets are designed for a door thickness range of 1-3/8" to 1-3/4". Measure the actual thickness of your door slab — at the edge, midpoint of the door height — with a tape measure or calipers.
- 1-3/8" — standard interior door
- 1-3/4" — standard exterior door; also used for premium interior doors
If your door is thicker than 1-3/4" — common in solid hardwood custom doors or some European imports — you will need a thick-door extension kit, which replaces the spindle with a longer one. Ask your hardware supplier before ordering.
The faceplate: a fifth measurement worth taking
The faceplate is the rectangular metal plate on the edge of the door that surrounds the latch opening. If you are replacing an existing latch in an existing mortise, the new faceplate should match the dimensions of the old one — otherwise you will have a visible gap around the faceplate where the old mortise extends beyond the new plate. Standard faceplates are 2-1/4" × 1" or 2-3/8" × 1-1/8". Measure the existing mortise opening before ordering.
Write it down before you order
When you contact a hardware supplier or place an online order, you should have:
- Backset: 2-3/8" or 2-3/4"
- Bore hole diameter: typically 2-1/8"
- Cross-bore diameter: typically 1"
- Door thickness: 1-3/8" or 1-3/4" (or actual if non-standard)
With these four numbers, any qualified hardware supplier can confirm compatibility before anything ships. It takes two minutes and eliminates the most common return reason in our industry.
Need help measuring or confirming compatibility? Contact our team — we walk customers through this process every day. Or bring your measurements to our Oakville showroom and we will check compatibility in person.
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Questions about your project? We are always happy to talk hardware.
