When you lose a key, move into a new home, or your ex-tenant still has a copy, the same question always surfaces: rekey the lock or replace it entirely? Many homeowners default to swapping the whole lock because they don’t understand how rekeying works, but that can cost you more than necessary without improving security. Meanwhile, others rekey a lock that’s actually worn out or compromised, leaving their front door vulnerable to picking or key duplication. This deep dive will walk you through the mechanics of pin tumblers, the true cost difference between rekeying and replacing, and the edge cases where only a full replacement makes sense—so you can make an informed decision and avoid wasting money or exposing your home to risk.
To understand rekeying, you need to know what’s inside a standard pin tumbler lock. The cylinder contains a plug that rotates when the correct key is inserted. Along the plug and the cylinder housing are paired holes, each holding two springs and two pins: a key pin (bottom) and a driver pin (top). When you insert a key, the cuts on the key push the key pins up to the shear line—the boundary between plug and housing—allowing the plug to spin. If the wrong key is used, at least one pin straddles the shear line, and the plug stays locked.
Rekeying works by swapping out the key pins so that a different key lifts them to the correct height. The driver pins and springs stay the same. For example, if your current key pin for a #5 cut is 0.030 inches tall, a new key with a #3 cut needs a taller pin to align at the shear line. A rekeying kit includes a set of pins of varying lengths, a plug follower, and a removal tool. With about 20 minutes and a bit of patience, you can change the pins to match any new key.
H3: What Rekeying Does NOT Change
This means rekeying is purely a credential change, not an upgrade. The lock’s resistance to picking, bumping, or brute force remains exactly as it was before.
The most common reason to rekey a lock is that you don’t know who still holds a key. That includes moving into a new house, after a roommate moves out, or after a contractor finishes a job with your spare. In these scenarios, the lock itself is usually in good working order—doors close smoothly, the bolt extends fully, and the key turns without sticking. Rekeying is the ideal fix because it secures the home without the expense of replacing hardware that functioned perfectly.
Another overlooked situation is when you want all doors to use the same key. Many builders install different keyways for each exterior door, which forces you to carry multiple keys. A locksmith can rekey all cylinders to match one key, provided they share the same keyway brand. For example, if your front door is a Schlage and the back door is a Kwikset, you can still rekey both, but you’ll need keys for each, or you can replace one cylinder to match the other brand. Rekeying is also cost-effective when you’ve lost a key and worry it might be found—you can rekey just that lock, or all locks if you’re unsure which one that key fits.
Tenant turnover is another clear-cut case for rekeying. As a landlord, you’re required to ensure previous tenants can’t enter. Professional locksmiths charge between $15 and $30 per lock for rekeying, plus a service fee that often runs $50–$100 for a trip. If you have three locks, that’s roughly $100–$150 total. Replacing three locks with new deadbolts would cost $75–$150 just for labor, plus $20–$60 per lock in hardware, putting the total well above $200. The savings are even greater if you do the rekeying yourself with a $10 kit.
Rekeying won’t fix a lock that’s mechanically failing. If the key sticks or requires wiggling, if the plug turns hard even with the correct key, or if the bolt doesn’t fully retract, those are signs of worn internals. Over time, springs loose tension, key pins wear down unevenly, and the plug itself can develop burrs from high-usage. Attempting to rekey a worn cylinder is like changing the oil on an engine with a blown gasket—you’ll still have bigger problems.
Another non-negotiable replacement trigger is after a break-in where the lock was attacked. If the lock face is scratched, the housing is bent, or the bolt doesn’t align smoothly, the structural integrity is compromised. Even if it looks okay, internal damage from a battered strike plate or twisted bolt could cause it to fail later. Don’t risk a package thief or intruder who knows the lock is weak—replace it entirely.
Security upgrades also call for replacement. If your existing lock is a standard pin tumbler from the 1980s, rekeying it won’t add high-security features like sidebars, anti-bump pins, or drill resistance. Weigh the cost of a new lock against the value of what’s inside your home. For entry points, a new ANSI Grade 1 deadbolt—like the Schlage B60N or Kwikset 980—runs $40–$80 and offers superior strength and pick resistance compared to any rekeyed old lock.
Let’s compare the expenses on a standard three-exterior-entry-home (front, back, garage door). I’ve pulled average prices from local hardware stores and national locksmith chains to give you a realistic picture.
Rekeying by a professional:
DIY rekeying with a kit:
Replacing all three locks with new deadbolts:
The numbers make rekeying the clear winner for pure cost, but only if the old locks are physically sound and meet your security needs. If the lock is damaged or you’re upgrading to a smart lock, replacement becomes the better value over time. In that case, get a smart lock like the August Wi-Fi Smart Lock (about $150) that fits over your existing deadbolt—it combines the convenience of keyless entry without necessarily replacing the bolt, though you’ll still need to rekey the manual backup cylinder.
Master key systems allow one key to open multiple locks, but each lock still has its own unique key. This is common for rentals, Airbnb hosts, and large homes. In a master key scenario, rekeying is more complex because the locksmith must install master pins under the driver pins. For example, a lock with a #5 cut might require a master pin of 0.015 inches to allow both the tenant’s key and the owner’s master key to work. This is a job for a professional—DIY kits rarely include master pins, and getting it wrong means the lock won’t operate.
Similarly, if you have a mix of brands across your doors—say, a Schlage front door and a Kwikset back door—rekeying all to one key may not be possible without replacing one cylinder. Each brand uses a different keyway, so a Schlage key won’t physically enter a Kwikset cylinder. In this case, you have three options: replace the less-used lock with the same brand as the other, rekey each with its own key (but then you’re back to two keys), or stick with separate keys. Many homeowners accept two keys to save on replacement costs, but if convenience matters, replacing one lock is worth the $25.
For those moving into a house with existing locks, always rekey immediately—even if the real estate agent gave you a key, there’s no knowing who else had access during showings. Many locksmiths offer a “rekey all locks” package that includes a matched set of keys, which is the safest and most efficient route.
If you’re comfortable with basic tools and have a spring for detail, rekeying a deadbolt is a rewarding DIY project. I’ll outline the process for a typical Kwikset or Schlage pin tumbler. Always purchase a rekey kit that matches your lock brand—the pin sizes and key blanks differ.
First, remove the lock from the door. Unscrew the two bolts on the interior side, then pull out the two halves. Use the plug follower (a metal tube that comes with the kit) to remove the cylinder plug carefully. Test the following steps on a table with good lighting.
Once the plug is out, push the follower from the bottom to eject the plug. You’ll see the key pins inside the plug’s chambers. Use the removal tool or tweezers to take them out. Then, insert the new key into the plug and note which cuts correspond to which chambers. Select the new key pins from the kit—each pin is marked with its number. For example, a #1 cut might use a 0.095-inch pin, while a #6 uses a 0.015-inch. Place the correct pin in each chamber, then reinsert the plug into the cylinder. The driver pins and springs stay in the housing by the retainer, but some kits require you to install them first—follow your kit’s instructions.
Finally, test with the new key—it should turn smoothly without excessive force. If the key sticks or won’t go in, you probably swapped two pins. Disassemble and start over.
Before diving into rekeying, verify compatibility. The keyway is the side profile of the key, and it defines which blanks fit. Kwikset uses the KW1 keyway; Schlage uses the SC1. A rekey kit for Kwikset won’t work on a Schlage cylinder because the pins might be a different diameter and the key blanks won’t insert. Additionally, some high-security locks like Medeco or Mul-T-Lock have patented keyways that require specialized dealer tools—these should always be rekeyed by a professional.
Here’s a quick checklist before you purchase a kit:
SmartKey systems are a notable exception. Schlage SmartKey deadbolts allow you to rekey without removing the lock. You insert the current key, turn to the “rekey” position, insert the new key, and turn back—the internal sidebar aligns to the new cuts in under a minute. This is faster than traditional pin swapping, but it only works on SmartKey-compatible locks. If you have one, rekeying is nearly effortless.
Smart locks add convenience but don’t eliminate the need for physical security. Most smart deadbolts (like August Smart Lock Pro) mount on your existing deadbolt, so the cylinder remains in place. This means you can rekey the cylinder to match your other locks, while the smart feature lets you use a keypad or phone. If you wish to change access codes, you don’t need to rekey—just update the app. But if you’re worried about someone with a physical key, rekeying the cylinder (if it’s a compatible brand) is easy.
One nuance: some smart locks come with a separate cylinder that may have a different keyway from your other locks. For instance, the August lock uses a Universal Mortise Cylinder that can be rekeyed, but you might need to order a specific cylinder to match your existing key. Before buying a smart lock, check whether it supports a cylinder that can be rekeyed. Many Yale and Schlage smart locks have a standard cylinder, while others require proprietary ones. If you have all Kwikset locks, look for smart locks that accept Kwikset keyways.
Certain situations demand full replacement regardless of cost. Rekeying an old lock that’s been compromised physically—like one with a bent bolt or broken spring—is pointless. Also, if you’re upgrading to meet insurance requirements—some policies require deadbolts on all exterior doors—an old lock might not meet ANSI Grade 1 standards. Lastly, if the lock is from a brand that’s discontinued or uses obsolete security features (like the classic pin tumbler from the 1970s), replacement is the smarter route.
Don’t forget about the strike plate and bolt. Even if you rekey, a weak strike plate won’t protect against a kick-in attack. Consider upgrading the strike plate to a reinforced one (like the Door Armor MAX) and installing longer screws (3 inches) into the door frame. These upgrades are inexpensive ($10–$20) and dramatically improve security—something rekeying alone can’t do.
When replacing, consider picking a high-security keyway that’s restricted—meaning keys can only be duplicated by authorized dealers. This prevents tenants or strangers from copying your key at a local hardware store. Schlage’s Primus and Medeco are common options, but they cost $80–$200 per cylinder. If that’s out of budget, at least choose a lock with anti-bump pins and a hardened steel bolt.
Here’s how I decide whether to rekey or replace. Ask yourself three questions: Is the lock in good mechanical condition? Is the brand and keyway something you want to keep? Do you currently have a legitimate reason to change keys (lost, unknown copies)? If the answer is yes to all three, rekey. If the condition is questionable or you’re upgrading security level, replace. If you’re unsure and the lock is more than 10 years old, spend the $40 on a new deadbolt—it’s better to start fresh.
Always keep the old lock with a label if you rekey, in case you forget the keyway later. And when you replace, use locks that are keyed alike—meaning you can use the same key for all doors. Many brands sell multi-pack deadbolts with matching keys, which saves money. If you’re a landlord, keep track of the key codes; a locksmith can rekey all uni
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