How to Choose a Smart Lock: Six Decisions, in Order

How do I choose a smart lock?

Choose a smart lock by working through six decisions in order: whether you replace the whole deadbolt or retrofit the inside only, whether it fits your door, how you want to unlock, how it connects, how it is powered, and whether the maker publishes a BHMA grade. Match those to your door and household, not to a feature list.

The reason to go in this order is that the early decisions are hard constraints and the late ones are preferences. If you rent, install type rules out most of the catalog before you have looked at a single fingerprint reader. If your door is non-standard, fit rules out more. Preferences like which unlock method you love only matter among the locks that survive the constraints. This guide lives under the guides hub; work down the six and the roundup you should land on becomes obvious.

1. Install type: full replacement or interior retrofit

This is the first fork and it removes the most options. A full deadbolt replacementtakes out your existing deadbolt entirely and installs a new lock body, keypad, and interior escutcheon in its place. You own the outside of the door, so you get an exterior keypad, a fingerprint reader, or a tap-to-unlock pad — the features most people picture when they picture a smart lock. The Yale Assure Lock 2, the Schlage Encode Plus, and the eufy Smart Lock C220 are all full replacements.

An interior-only retrofitleaves your existing deadbolt in place and clamps a motor over the inside thumbturn to turn it for you. The exterior of the door does not change at all, and you keep your existing key and cylinder. That makes it the answer for renters and anyone who cannot modify the door: nothing is drilled and the original hardware goes back on at move-out. The SwitchBot Lock Pro is the retrofit here. The trade-off is equally clear — there is no exterior keypad in the box, and the motor is only as reliable as the deadbolt underneath it, so a stiff bolt that already needs a shoulder against the door will jam a retrofit. If you rent or will not touch the door, the shortlist is retrofits; the field is ranked in our no-drilling renters roundup.

2. Door fit: backset, cross-bore, thickness

A full-replacement lock has to physically fit your door, and three measurements decide it: the backset (edge of the door to the center of the bore, standardized at 2-3/8 in or 2-3/4 in), the cross-bore diameter (2-1/8 in on modern doors, but 1-1/2 in on some older ones, which is a hard stop), and the door thickness (1-3/8 in to 1-3/4 in is the normal supported range; thicker doors need an extension kit). Most builder-grade doors from the last forty years match all three, but the ones that do not cause the majority of smart-lock returns.

Two things follow. First, measure before you order and check the number against the model's install manual, not the marketing copy — the full procedure is laid out in our guide to whether a smart lock fits your door. Second, this is the other reason a retrofit is the safe answer when your measurements come back non-standard: because it drives your existing deadbolt rather than replacing it, backset, bore, and thickness stop mattering entirely.

3. Entry methods: key, code, fingerprint, phone, auto-unlock

Now the preferences begin. A smart lock can offer several ways in, and households rarely agree on one, so the practical move is to list who lives there and how each of them will want to unlock the door.

• Physical key. A keyed lock keeps a mechanical cylinder as a fallback, which matters if you hand a key to a contractor or want a non-electronic way in. The keyed Yale Assure Lock 2 retains this; some minimalist locks drop the keyway on purpose.
• Code / keypad. A touchscreen or button keypad lets anyone in with a PIN and no phone, and codes keep working with the internet down. This is the workhorse method for families and guests. If a keypad is the priority, start from our best smart locks roundup, which leads with keypad-equipped full replacements.
• Fingerprint.A reader unlocks in well under a second with nothing to remember or carry — the fastest method for regular users. The eufy Smart Lock C220 is the budget route into fingerprint; the field is ranked in our fingerprint door locks roundup.
• Phone / tap-to-unlock. Bluetooth proximity or a tap-to-unlock pad (the Schlage Encode Plus supports Apple Home Key, so an iPhone or Apple Watch tap opens it) suits people who always have a phone and never a code in memory.
• Auto-unlock. The lock senses your phone approaching and unlocks hands-free. Convenient with an armful of groceries, but worth confirming it re-locks reliably, since a geofence that misfires is the most common complaint about the feature.

4. Connectivity: Bluetooth, Wi-Fi, Thread/Matter — and what works offline

Connectivity decides what the lock can do when you are not standing at the door, and the three common radios behave very differently. Bluetoothonly reaches a phone within range, so a Bluetooth-only lock is excellent at the door and unreachable from work unless a hub carries it — which is exactly the SwitchBot Lock Pro's arrangement, where remote access runs through a SwitchBot hub rather than the lock itself. Wi-Fi built into the lock gives you remote control with no bridge to buy or power, as on the eufy C220, at the cost of being the heaviest possible battery draw. Thread and Matterconnect the lock into a cross-brand smart-home fabric through a hub, with low power draw and vendor independence; the Yale Assure Lock 2's swappable radio module means a Matter upgrade is a card swap rather than a new lock.

The point most buyers miss: the core functions of a good lock — codes, fingerprint, the keypad, manual operation — keep working with the internet completely down, because the radio only carries remote access and notifications. Connectivity is about reach, not about whether the door opens. If remote unlocking and whether a lock needs the internet is the live question for you, read whether smart locks need Wi-Fi before you weigh the radios.

5. Power and battery reality

Almost every residential smart lock runs on batteries, and the radio you chose in step four largely sets how long they last. A built-in Wi-Filock keeps its radio awake to stay reachable, which is the heaviest drain — the eufy C220's own record calls this out, and you should expect shorter runs from any always-on Wi-Fi lock. A Bluetooth or Thread lock sips far less and goes proportionally longer between changes. Cell type matters too: most full replacements take 4x AA alkalines, some take more for a bigger reservoir, and a retrofit like the SwitchBot Lock Pro uses a rechargeable pack instead of a steady diet of disposables.

Two things make battery life a non-event rather than a chore. First, every credible lock warns you well before it dies, so you are replacing cells on a schedule, not getting locked out. Second, a well-aligned strike halves the work the motor does; a lock fighting a misaligned bolt on every cycle drains far faster than the spec suggests. Fix the door before you blame the battery.

6. The published BHMA grade

The last decision is the one buyers skip and should not: does the manufacturer publish a BHMAgrade for the lock? The Builders Hardware Manufacturers Association grading (Grade 1, 2, or 3) rates a lock's physical durability and security against a published standard — cycle counts, bolt strength, and forced-entry resistance. It is not a marketing number a brand assigns itself; it is a third-party benchmark, and a lock that carries a grade has been measured against it.

The catch is that most smart-lock brands do not publish one, which is why it is a genuine differentiator when a brand does. Schlage's deadbolt line is the reference point for BHMA Grade 1 in residential locks, and the Encode Plus inherits that pedigree — if a published grade on the lock body matters more to you than any smart feature, that is where it leads. When no grade is published, weight the mechanical basics you can see: a solid metal bolt, a full 1 in throw, and a reinforced strike do more for real-world security than any electronic feature.

The six decisions as a matrix