Backset is the horizontal distance measured from the edge of the door to the center point of the hole that houses the lock cylinder, knob spindle or lever mechanism. It is not the overall size of the lock, the thickness of the door, or the height at which the lock is installed — it specifically describes how far the lock body sits from the door's edge.
Backset matters because it must match the holes already drilled into a door, or the holes a door is about to be drilled to. A lockset with the wrong backset will not seat correctly even if every other specification — grade, finish, certification — is exactly right. For replacement projects in particular, backset is often the single detail that determines whether a new lockset installs in minutes or requires redrilling the door.
The two most common metric backset sizes are 60mm and 70mm. A 60mm backset is standard on most residential doors and many light commercial doors, placing the cylinder relatively close to the door edge. A 70mm backset is more common on wider door stiles, heavier commercial doors, and certain European door profiles where the extra distance accommodates a wider lock body or additional hardware.
In markets that use imperial measurements, the equivalent common sizes are typically referenced as 2-3/8 inch and 2-3/4 inch, which are close to but not identical to the 60mm and 70mm metric sizes. When sourcing for a project that mixes suppliers or markets, confirm which measurement system the existing door hardware was specified in before assuming a direct metric-to-imperial match.
To measure backset on an existing door, measure horizontally from the edge of the door face to the center of the hole where the current cylinder or knob sits. A tape measure or ruler is sufficient — the key is measuring to the center of the hole, not to its near or far edge, since that is the reference point lock manufacturers use.
For a replacement or renovation project spanning multiple doors, it is worth measuring more than one door rather than assuming uniform backset across the property. Buildings renovated in phases, or supplied by more than one hardware vendor over time, frequently end up with mixed backset sizes even when the doors look identical from the hallway.
Backset works alongside door thickness as a second, equally important compatibility check. A lock body sized correctly for backset can still fail to install properly if the door thickness falls outside the range the latch and strike components were designed for. Standard interior and exterior doors generally fall within a common thickness range, but fire-rated doors, glass doors and some specialty commercial doors can sit outside that range and require a specific lock body variant.
Some lockset designs offer an adjustable backset — commonly switchable between 60mm and 70mm on the same unit — which reduces the risk of a mismatch when the exact door spec is uncertain at the time of order. This is worth asking about specifically during RFQ if the project has not been field-measured yet.
Typical backset sizes mapped to the door types and markets they are most commonly specified for.
| Backset Size | Common Region / Door Type | Notes |
|---|---|---|
| 60mm | Residential and light commercial, most common metric size | Confirmed per SKU |
| 70mm | Heavier commercial doors, wider stiles, some EU profiles | Confirmed per SKU |
| 2-3/8 in (≈60mm) | US residential, imperial-sized doors | Not an exact metric match |
| 2-3/4 in (≈70mm) | US commercial, imperial-sized doors | Not an exact metric match |
| Adjustable 60/70mm | Mixed-spec projects, uncertain field measurement | Available on select lock bodies, confirmed per order |
On a single-unit replacement, a backset mismatch is a minor inconvenience — the wrong part gets returned and a correct one ordered. On a bulk project order, the same mismatch scales directly with volume, and because standard MOQ for custom or branded lock bodies commonly runs in the 500 to 3,000 piece range, a corrective re-order is neither fast nor cheap. This is why backset should be confirmed against a physical sample or a verified architectural drawing before a bulk purchase order is placed, rather than assumed from a product listing photo.
For projects sourcing across multiple door types — some 60mm, some 70mm, some requiring adjustable bodies — it is common to request a small pilot batch, typically in the 50 to 200 piece range, confirm fit on site, and then place the full bulk order against the confirmed spec. This two-step approach is slower than a single large order but meaningfully reduces rework risk.
Send door type, measured backset and target volume — LatchHub will confirm the matching lock body across partner factories and propose a pilot-to-bulk sourcing plan.
Request a QuoteBackset confirms fit; grade confirms performance. Both are needed before ordering.
Read guide →The companion hinge standard for projects also sourcing hinges alongside locksets.
Read guide →Once fit and grade are confirmed, finish is the next specification to lock in.
Read guide →