Backset is one of the first measurements you need before ordering any door lock — smart or traditional. Get it right and the lock drops straight in. Get it wrong and you are looking at a return, a reorder, and a delayed installation.

It is a simple measurement to take, but the consequences of skipping it or guessing are surprisingly common. This guide covers everything you need:

• What backset is and exactly where to measure it
• How to take the measurement correctly on any door
• Standard backset sizes used in Australia
• What happens when the backset does not match your lock
• Which backset applies to smart locks, mortice locks, and tubular hardware

This guide sits alongside Chapter 02 — Measuring Your Door in the Smart Lock Buyer’s Guide, which covers the full set of measurements needed before selecting any smart lock.

This guide was reviewed and updated in May 2026.

What Is Backset?

Backset is the horizontal distance from the edge of the door to the centre of the spindle hole — the hole through which the door handle spindle passes. It is measured from the door edge (not the door frame, not the face of the door) to the exact centre of that hole.

It is called “backset” because it describes how far back from the edge of the door the lock mechanism sits. The latch bolt, the spindle, and the cylinder all position themselves relative to this measurement.

Measure to the centre, not the edge. A common mistake is measuring to the edge of the existing handle escutcheon or rose rather than to the centre of the spindle hole. The spindle centre is what the lock manufacturer specifies against. If you measure to the wrong point, even by 5mm, the new lock will not align correctly.

How to Measure Your Backset

Step 1 — Open the door. You need clear access to the door edge where the latch bolt sits. The measurement is taken from the face of the door edge (the narrow edge of the door, not the flat face), so the door needs to be open and accessible.

Step 2 — Find the centre of the spindle hole. Look at the door edge and locate the latch bolt. Directly above or below (depending on the lock) is the spindle hole — the circular hole through which the square handle spindle passes. Mark or identify the exact centre of this hole.

Step 3 — Measure horizontally. Place your tape measure at the face of the door edge and measure horizontally to the centre of the spindle hole. Keep the tape level — this is a horizontal measurement only, not diagonal. The number you read is your backset.

Step 4 — Check against the standard sizes. In Australia, the result should be 60mm, 70mm, or 44mm for most locks (see the next section). If your measurement does not land near one of these figures, double-check that you measured to the spindle centre and not to the edge of the handle rose.

The image below demonstrates the measurement technique on a real door — and as you can see, this particular door has a 40mm backset. That is a good reminder that you cannot assume your door is 60mm. While 60mm is the most common backset for Australian residential smart lock installations, backsets in Australia range from as little as 22mm up to 127mm depending on the lock type, door format, and application. The only way to know your backset is to measure it.

No existing lock to measure from? If you are measuring a new door with no hardware yet fitted, measure from the door edge to the centre of the pre-drilled spindle hole in the door face. The hole is already there — you just need to find its centre.

Standard Backset Sizes in Australia

Australian doors are not all the same, and neither are the locks that fit them. These are the backset sizes you will encounter in practice:

60mm is the most common backset for Australian residential smart locks — but it is not universal. As the table above shows, backsets in use across Australia range from 22mm to 127mm. The majority of smart locks sold in Australia are designed for 60mm, which covers most standard residential timber and aluminium doors. However, your door may not be 60mm. The only way to confirm is to measure it.

Adjustable backset locks. Some tubular latches — particularly entry-level models — offer an adjustable backset, most commonly switchable between 44mm and 57mm, or between 60mm and 70mm. These are convenient for retrofits where the existing hole pattern falls between the standard sizes. Check the product specification before assuming a lock is adjustable.

What Happens When the Backset Is Wrong

A mismatched backset is one of the most common reasons a new lock cannot be installed without modification. Here is what happens in practice depending on the direction of the mismatch:

Smart locks are not adjustable once ordered. Unlike some traditional tubular latches, smart lock mechanisms are fixed to a specific backset. There is no field adjustment. If the backset is wrong, the lock goes back. Measure before you order — every time.

Backset errors are one of the most common installation mistakes covered in our guide to DIY smart lock installation errors. That post covers the full set of fitment checks worth completing before drilling anything.

Backset and Smart Locks — What to Know

Every smart lock in the Australian market is specified to a fixed backset. For the majority of residential smart locks, that backset is 60mm. For ANSI mortice-format smart locks (used in commercial applications and aluminium-framed doors), it is typically 70mm.

The full measurement checklist. Backset and bolt throw are two of the six measurements covered in Chapter 02 — Measuring Your Door of the Smart Lock Buyer’s Guide. If you are preparing for a smart lock installation, that chapter walks through the complete pre-purchase measurement process.

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Not Sure About Your Backset?

Send us a photo of your door edge and existing hardware — our team can confirm your backset and recommend the right lock before you order.