How to Replace a Deadbolt Yourself (and When to Call a Locksmith Instead)
Replacing a standard single-cylinder deadbolt is genuinely a DIY job for most homeowners — no special tools, about 20 minutes once you've got the right replacement in hand. Here's the actual process, the measurements that trip people up, what to have on hand before you start, and where it stops being a DIY job.
Before you buy: measure twice
Two measurements decide whether a replacement deadbolt drops straight in or fights you the whole way:
| Measurement | What it is | Standard sizes |
|---|---|---|
| Backset | Distance from the door edge to the center of the bolt hole | 2-3/8" or 2-3/4" — most new deadbolts ship adjustable between both |
| Door thickness | Thickness of the door itself | 1-3/8" (interior-weight) or 1-3/4" (standard exterior) — confirm the deadbolt's screw length matches |
| Cross bore diameter | The large hole through the door face | 2-1/8" is standard on nearly all pre-drilled residential doors |
| Edge bore diameter | The hole through the door edge for the bolt mechanism | 1" is standard |
Measure the backset from the door edge to the center of your existing bolt hole before buying — it's the one measurement that isn't always adjustable after the fact. While you're at it, pick the grade deliberately rather than grabbing whatever's cheapest — see what grade you actually need. This is the moment to upgrade from a Grade 3 builder-grade bolt to Grade 2 or Grade 1 if the door in question is an exterior door.
What to have on hand
- A Phillips screwdriver (nearly all residential lock hardware uses Phillips screws)
- A tape measure, for the backset and thickness checks above
- A pencil, if the new strike plate doesn't align perfectly with the old mortise and needs re-marking
- A chisel, only if you're installing a box strike or the new strike plate is a different size than the old mortise
- 3" wood screws, to replace whatever ships in the box for the strike plate (see anti-theft door upgrades for why this matters)
The 20-minute replacement
- Remove the interior and exterior escutcheons. Unscrew the two mounting screws on the interior side; both halves come away from the door.
- Remove the latch/bolt assembly. Two screws on the door edge holding the faceplate; the bolt mechanism slides out of the door.
- Check the bolt-hole and edge-bore diameter match the table above — nearly all pre-drilled doors are standard, so a new deadbolt usually drops straight in.
- Insert the new bolt assembly, aligned so the bolt extends and retracts smoothly by hand before you screw anything down.
- Attach the exterior half through the bolt mechanism, then the interior half (thumbturn) from the inside, and secure both mounting screws — snug, not overtightened, which can bind the mechanism.
- Install the new strike plate — and don't stop at the screws in the box. Swap in 3" screws that reach the framing stud.
- Test with the door open first, then closed, before you consider it done. The bolt should throw and retract smoothly with no scraping or binding.
Common mistakes that turn a 20-minute job into an hour
- Overtightening the mounting screws before confirming the bolt moves freely — this is the single most common cause of a "new lock feels stiff" complaint, and it's a reinstall issue, not a defective lock.
- Installing the latch/bolt assembly upside down. Most bolts have a directional bevel and will still physically install backwards, then bind or fail to fully retract. If the bolt doesn't sit flush when extended, pull it and flip it.
- Skipping the "test with the door open" step and only discovering an alignment problem once everything is fully installed and the door is closed.
- Assuming the old strike plate mortise fits a new box strike without checking — box strikes are typically wider than a standard strike plate and need the mortise enlarged first.
DIY vs. professional: what it actually costs
| Typical cost | Time | |
|---|---|---|
| DIY replacement (parts only) | Cost of the new deadbolt, roughly $25–150+ depending on grade and brand | ~20–30 minutes per door |
| Locksmith replacement (parts + labor) | Parts plus a service call fee | Similar per-door time, but scheduling adds a day or more |
| Locksmith rekey (existing lock, new key) | Usually less than full replacement | ~15–20 minutes per lock |
DIY replacement is the cheapest option when the lock genuinely needs replacing. When the existing hardware is fine and only the key needs to change, a rekey is usually the better value than full replacement either way — see when to call a locksmith vs. DIY.
When to call a locksmith instead
- The door wasn't standard-bored — older homes, non-standard hardware, or a mortise lock (common in older, higher-end doors) require different tools and a different installation entirely.
- You want to rekey rather than replace — matching a new exterior lock to your existing key, or consolidating multiple doors to one key, is locksmith work.
- The strike plate area is already damaged from a prior forced-entry attempt or rot, and needs real carpentry, not just longer screws.
- You're moving into a home with an unknown key history — see rekeying a new-build home.
FAQ
Can I reuse my existing key with a new deadbolt?
Only if a locksmith rekeys the new lock's cylinder to match your existing key — a new deadbolt out of the box comes with its own new keys, unrelated to your old ones.
What if my new deadbolt's backset doesn't match my door?
Most modern deadbolts ship with an adjustable latch that telescopes between 2-3/8" and 2-3/4" — check the specific product before buying if your door falls outside that range.
Do I need to replace the strike plate every time I replace the deadbolt?
Not strictly, if the existing strike plate is in good condition and properly aligned — but it's the ideal moment to upgrade to longer screws or a box strike while everything is already apart.
What if the new deadbolt feels stiff right after installation?
Almost always an overtightened mounting screw rather than a defective lock — back the interior mounting screws off slightly until the bolt throws and retracts smoothly, then confirm they're still snug enough that the escutcheon doesn't wobble.
How do I know if my door has a mortise lock instead of a standard bored lock?
A mortise lock has a single large rectangular pocket cut into the door edge housing both the latch and deadbolt in one unit, versus two separate round holes for a bored lock. If you see one rectangular cutout instead of two round ones, it's a mortise lock — call a locksmith rather than buying a standard replacement.
Can I upgrade the grade without changing the backset or bore size?
In most cases yes — grade is a function of the internal mechanism and materials, not the physical dimensions, so a Grade 1 replacement generally fits the same standard bore and backset as the Grade 3 unit it's replacing.
What finish should I choose, and does it affect security?
Finish (brass, nickel, bronze, matte black, and so on) is purely cosmetic and has no bearing on the ANSI/BHMA grade or security performance underneath — choose based on matching the door's existing hardware rather than any security consideration.
For the fuller decision framework on cost and when professional help pays for itself, see when to call a locksmith vs. DIY.