Mastering Door Backset Measurement: A Simple Guide

Door hardware has gotten unnecessarily confusing with all the conflicting advice and mismatched product descriptions flying around online. As someone who has replaced locksets on probably fifteen doors across two houses, I learned everything there is to know about backset measurement — mostly because I bought the wrong hardware twice before I understood what I was actually measuring. Today, I will save you that particular frustration.

I’m apparently the kind of person who measures things three times before cutting and still second-guesses myself at the hardware store. The 2-3/8 inch backset works for every interior door in my house, while 2-3/4 inches is what my front door needs. Getting that backwards is exactly as annoying as it sounds.

What Is Backset, Actually

The backset is the distance from the edge of the door to the center of the borehole — the large hole where your lockset or handle apparatus passes through. This measurement determines which hardware will fit your door. Get it wrong and the latch won’t line up with the strike plate on the door frame, which means a door that either won’t close properly or won’t latch at all.

That’s what makes backset one of those measurements that matters to us homeowners — it’s the difference between hardware that works perfectly and an afternoon of profanity.

Most residential doors use one of two standard measurements: 2-3/8 inches or 2-3/4 inches. Interior doors and hollow-core doors almost universally use 2-3/8 inches. Exterior doors, particularly older or heavier ones, often use 2-3/4 inches.

Probably Should Have Led with This Section, Honestly

Before you buy anything, measure your existing backset. If you’re replacing existing hardware, the current backset is your answer. Many locksets are sold as “adjustable backset” and can be configured for either standard measurement, which takes the guesswork out of it entirely. Check the product specs before purchasing.

What You Need

• Measuring tape or ruler
• Pencil or marker for marking the center point if needed
• Notepad to record the measurement

That’s genuinely the entire tool list. This is one of the easier measurements in home improvement.

How to Measure

Start by locating the borehole — the large circular cutout where the handle or lock mechanism goes. Place the end of your measuring tape flat against the edge of the door (the narrow face that meets the door frame, not the flat face of the door). Extend the tape to the center of the borehole. That number is your backset.

Double-check it. Measure from the door edge to where the lock cylinder sits in the center of the borehole. It’s easy to accidentally measure to the near edge of the borehole rather than the center, which will throw your measurement off by about an inch and send you in the wrong direction at the hardware store.

Non-Standard Backsets

Custom doors, very old doors, and some imported European doors occasionally have backsets that don’t match either standard. If you measure 2-1/2 inches or some other non-standard number, you’re probably looking at an older door or a specialty installation. Adjustable backset latches exist specifically for this situation — they can accommodate a range of measurements and are worth the modest extra cost.

When the Latch Doesn’t Line Up

If your door hardware seems misaligned after installation, backset is the first thing to recheck. Measure again from the exact edge of the door to the borehole center. Small errors in measurement compound once everything is installed. The strike plate position on the door frame is the second thing to check — sometimes the fix is simply adjusting the strike plate a quarter inch rather than replacing the hardware entirely.

A Note on Borehole Size

While you’re measuring backset, also verify that your borehole diameter matches your new hardware. Standard residential boreholes are 2-1/8 inches in diameter. If yours is smaller, you’ll need to enlarge it with a hole saw before the new hardware will fit. This is a separate issue from backset but worth confirming before you get deep into an installation.

Measure your backset before you leave for the hardware store, write it down, and you’ll avoid one of the most common and most annoying mistakes in door hardware replacement. The rest of the installation is straightforward from there.