If you’ve ever tried installing or replacing a door lock, you might have come across the term “backset.” It sounds technical, but don’t worry—it’s easy to understand and super important for getting your lock to fit and work correctly.
In this guide, we’ll break down what a backset is, why it matters, how to measure it, and what to look for when buying a new lock.
What Exactly is a Backset?
The backset is the distance from the edge of your door to the center of the hole where your doorknob or lock goes—also known as the borehole. Think of it like the spot where your lock “lives” inside the door. It might sound like a tiny detail, but this little measurement makes a big difference. Why? Because it helps your lock line up perfectly with the strike plate on the door frame. If your backset is off, your lock might not fit right, your door may not latch properly, or worse it might not lock at all.
Backset Sizes: What’s Standard?
These are the sizes you’ll find in nearly every modern home. Luckily, many lock manufacturers now offer adjustable latches that work with both backsets, making installation a breeze.
| Backset Size | Measurement (inches) | Used For |
| 2-3/8″ | 60 mm | Interior doors (bedroom, bathroom) |
| 2-3/4″ | 70 mm | Exterior doors, commercial doors |
Why Does the Backset Matter?
You might be wondering—does this tiny measurement matter that much? The answer is absolutely yes. The backset plays a big role in how well your door lock functions and fits. If the backset is too short or too long for your door, your lock might not line up properly with the hole in the door frame, also known as the strike plate. This can lead to problems like a sticky latch, a misaligned deadbolt, or even a door that won’t close or lock securely. In short, the right backset = better function + better fit.
How to Measure the Backset on Your Door
Measuring the backset on your door is super easy—and only takes a minute! Whether you’re replacing an old lock or installing a new one, knowing your backset helps you choose the right hardware and avoid installation headaches.
Here’s how:
- Open your door and look at the side edge (where the latch goes).
- Find the round hole (the borehole) where the knob or lock is.
- Measure from the edge of the door to the center of that hole.
That measurement—either 2-3/8” or 2-3/4”—is your door’s backset.
💡 Quick Tip: If you have the old latch, it might be stamped with the backset size already!
Adjustable Backsets: The Best of Both Worlds
Many modern locks now come with adjustable latches, which can switch between the two standard sizes with just a small slide or twist during installation. This means you don’t have to stress about measuring perfectly or buying the wrong lock. Whether you’re working on an old door, a new door, or multiple doors in one house, adjustable backsets give you the flexibility to get a perfect fit every time. They’re especially handy if you’re not sure which size your existing lock is, or if you’re doing a full home upgrade.
Buying a Lock? Here’s What to Check First:
Before you head to the local store or hit that “Add to Cart” button, it’s important to double-check a few key things. Choosing the right lock isn’t just about style or security—it’s also about making sure it fits your door perfectly, especially when it comes to the backset.
Here’s a quick checklist to guide you through the lock-buying process:
| Checklist Item | Why It Matters |
| Measure your backset | Ensures the latch lines up properly with your door frame |
| Know your door type | Interior and exterior doors may need different lock styles |
| Check for an adjustable latch | Gives you flexibility if you’re unsure of your backset size |
| Match door thickness | Standard is 1-3/8″ to 1-3/4″, but some locks support wider doors |
| Choose the right lock type | Deadbolt, knob, lever, keypad—pick based on your security needs |
| Read the product details | Look for backset size, compatibility, and included hardware |
FAQs
Q: Can I use a lock with a different backset than my door?
Not without modifying the door. It’s always best to match the backset.
Q: What happens if I use the wrong backset?
The knob or lock may not line up correctly, making it hard to close, latch, or lock the door.
Q: Do all locks have adjustable backsets?
No. Some only work with one size. Always read the product details before buying.
Final Thoughts
So there you have it—the backset is a small but mighty part of your door lock setup. It may just be a measurement, but it plays a big role in ensuring your lock works smoothly, aligns correctly, and keeps your home secure. Before your next installation or lock upgrade, grab a tape measure and check your door’s backset. A few seconds now can save you frustration later.
