How do I install a new door lock?

Short answer

Install a new door lock by measuring your door, choosing a lock that matches your backset and door thickness, removing the old hardware, installing the latch and exterior/interior assemblies, securing the strike plate, and testing for smooth operation. Most replacements take 20–45 minutes with basic hand tools; drilling fresh holes takes longer and benefits from a lock-installation jig.

What you’re installing and where it fits

Most residential doors use a cylindrical lock (knob/lever) and often a separate deadbolt. Replacement is straightforward if your door is already bored. Fresh installs (no holes yet) require careful measuring and drilling.

Common specs:
- Borehole (lockset): 2-1/8 in (54 mm)
- Cross bore (latch hole): 1 in (25 mm)
- Backset: 2-3/8 in or 2-3/4 in (adjustable on many locks)
- Door thickness: 1-3/8 in to 1-3/4 in (verify lock supports yours)
- Typical handle height: ~36 in from finished floor
- Deadbolt height: 6–8 in above handle

Tools and materials

• Phillips screwdriver (#2) and small flathead
• Tape measure, pencil, combination square
• Power drill/driver; bits: 1/8 in pilot, and possibly 1 in spade bit
• Chisel (3/4–1 in) and hammer (for mortising latch/strike if needed)
• Utility knife and masking tape
• Lock installation jig with hole saws (only for fresh bores)
• Wood shims, wood filler (optional for adjustments)
• Safety glasses and hearing protection

Step-by-step: replacing an existing lock (no new holes)

1. Verify fit
   • Check backset (2-3/8 or 2-3/4) and door thickness on the package. If it’s a lever, confirm handing (left/right) or choose a reversible model.
2. Remove the old lock
   • Open the door. Remove the interior handle/rose screws, then pull off both sides of the lock. Remove the two faceplate screws on the door edge and slide out the latch. For deadbolts, remove the interior thumbturn plate and screws, then the exterior cylinder.
3. Prep the latch
   • Set the backset on the new latch (many are twist-adjustable). Check the latch faceplate style: rounded corner vs. square. If your door mortise doesn’t match, swap to the included plate or lightly chisel the mortise to fit. The bevel of the latch should face the strike.
4. Install the latch
   • Insert the latch with the UP/top mark oriented correctly. Secure with the provided screws. Don’t overtighten—snug plus a quarter turn is enough.
5. Install exterior and interior assemblies
   • For a knob/lever: Insert the exterior spindle through the latch, align the interior side, and fasten the two long through-screws. For a deadbolt: Insert the keyed cylinder outside and thumbturn inside, aligning the tailpiece through the latch; fasten through-screws. Keep everything square and tighten evenly.
6. Fit the strike plate
   • If reusing the old strike, test operation first. If replacing, position the new strike over the existing mortise; adjust with a chisel if needed. Use 3 in screws on the hinge-side jamb holes to bite into the framing for security (especially for deadbolts).
7. Test and adjust
   • Close the door gently. Turn the knob/lever and thumbturn. The latch and bolt should extend and retract fully without rubbing. If the deadbolt binds, adjust strike position slightly. A dab of lipstick or chalk on the bolt helps mark the strike for fine-tuning.

Time: 20–45 minutes. Cost: $25–$60 (entry knob/lever), $30–$80 (deadbolt), $100–$300 (smart lock).

Fresh installation (door not bored)

• Use a lock installation jig with 2-1/8 in and 1 in hole saws. Mark heights, center the jig at the chosen backset, and drill the 2-1/8 in face bore first, then the 1 in edge bore. Drill halfway from each side for a clean hole. Mortise latch and strike plates with a sharp chisel. Then follow the replacement steps above.

Tip: Tape the door face where you’ll drill to reduce tear-out. Keep bits square to the surface.

Safety and best practices

• Wear eye protection and hearing protection while drilling/chiseling.
• Keep the door supported and hands clear of the bit path.
• Use the correct driver bit to avoid cam-out and stripped screws.
• Do not overtighten through-screws; it can bind the latch or crack trim.
• Use graphite powder or a PTFE lock lubricant on cylinders; avoid petroleum oils that attract dust.

Pro tips for smooth results

• Choose quality: ANSI/BHMA Grade 2 is solid for most homes; Grade 1 for high-traffic or max security.
• Reinforce the strike: On deadbolts, use 3 in screws into the stud for kick-in resistance.
• Check door alignment: If the door sags, tighten hinge screws or swap to longer hinge screws into framing before adjusting the strike.
• Smart locks: Confirm door thickness and bore size, and verify there’s clearance between the interior module and trim/casing.
• Rekeying: Many entry sets include a rekey feature (e.g., “smart rekey”). Match all exterior locks to a single key for convenience.

Common mistakes to avoid

• Wrong backset or latch orientation: An incorrect backset or upside-down latch causes binding.
• Misaligned strike: Don’t enlarge the strike hole excessively; adjust the door or move the strike in small increments.
• Mixing screws: Faceplate screws are often shorter/finer-thread. Using the wrong ones strips or protrudes.
• Ignoring door bevel: Latch face should sit flush; pare the mortise, don’t force the screws to pull it in.
• Skipping pilot holes: Especially in hardwood jambs; drill 1/8 in pilots to prevent splitting.

When to call a professional

• You have a metal or fiberglass door without existing holes and no jig.
• You’re replacing a mortise lock, multi-point lock, or hardware on a fire-rated or commercial door.
• The door/jamb is out of square, the bolt won’t align even after hinge and strike adjustments, or the frame is damaged.
• You need master-keying or complex rekeying beyond DIY kits.

With the right measurements, a decent screwdriver, and patience, most homeowners can swap a lock in under an hour. For fresh installs, a jig makes the drilling clean and accurate, and a locksmith can save time if you’re unsure.