How to Measure Your Door Before Buying a Smart Lock: 5 Numbers, 10 Minutes

Five numbers decide whether a smart lock fits your door: the door thickness, the backset, the distance between the handle and the keyhole, the flat space around the handle, and the gap between the door and the frame. Add which way the door swings and you’ve got everything a fitter needs. You need a tape measure, a screwdriver and about ten minutes.

Get those right and you buy once. Get one wrong and you’ll end up returning a lock, or paying someone to cut your door so it fits.

This is the at-the-door how-to. If you’re reading a product listing and want to know which of these numbers the seller should be giving you, read What Makes a Smart Lock a Bad Buy? If your door is aluminium with glass, our aluminium door fit guide covers the narrow-frame version of this. If you’ve already picked a Lockin, the handing question has its own post: Left Hand or Right Hand?

What do you need before you start?

• A steel tape measure in millimetres. A soft sewing tape bends and you’ll be off by a few mm.
• A Phillips screwdriver, if you want to take the inside handle off. You don’t have to, but it makes two of the measurements much easier.
• Your phone, for photos.
• The door open, and good light on the edge. In most Dubai apartments the corridor side is dim, so use your phone torch.

Measure the door itself, even if you’ve still got the old lock’s box or the developer’s spec sheet. Fit-outs in towers in JVC, Dubai Marina and Al Reem Island get changed between owners, and we regularly find a different lock body to the one in the handover pack.

Which five numbers decide whether a smart lock fits?

Then one direction, which isn’t a number: which side the hinges are on and whether the door opens towards you or away from you.

Numbers 2 and 3 together are what the trade calls the lock body size. A “6068” body has a 60 mm backset and 68 mm centres. A “5085” has 50 mm and 85 mm. They don’t swap. Your door already has one of them cut into it, and the lock you buy needs to match it or someone has to rout and re-drill the door.

How do you measure each one?

1. Door thickness

Open the door and put the tape across the edge, from the outside face to the inside face. Measure near the handle, not at the top, because some doors have a thicker lock rail.

Write the number to the millimetre. A smart lock page that’s worth buying from gives a range. The EZVIZ DL05 we stock, for example, lists 30 to 110 mm. If your door is 45 mm, you’re well inside. If you’re right at the edge of a range, tell us before you buy, because the spindle and bolts that come in the box are cut for the middle of the range, not the ends.

Steel doors and fire-rated timber doors in towers are often thicker than you’d guess, because of the core, so put the tape on them even if they look standard.

2. Backset

Measure from the door edge (the face the latch comes out of) to the centre of the handle spindle. If the handle is on, measure to the centre of the handle where it meets the door. If you’ve taken the handle off, measure to the centre of the square hole.

Common results:

• About 60 mm. A standard smart lock body like a 6068 will probably sit in the pocket.
• About 50 mm. Look for a lock that ships with a 50 mm body, or plan for a cylinder or retrofit route.
• 25 to 35 mm. You’ve almost certainly got a narrow-stile aluminium door. Go to our aluminium guide.

Measuring to the edge of the handle instead of the centre is the most common mistake we see. It puts you 10 to 15 mm short, which is exactly the difference between two lock body sizes.

3. Centre distance

Measure from the centre of the handle spindle down to the centre of the keyhole. On most doors the keyhole is below the handle.

If your number is 68 mm and your backset is 60, you’ve got a 6068. If it’s 85 and 50, a 5085. If it’s something else, write it down anyway. It still tells us what’s in the door.

Some villa doors have the cylinder above the handle, or a separate deadbolt with its own key. Measure every hole and say where each one sits.

4. Flat panel space

A full smart lock has a front panel and a rear panel, and both have to sit flat on the door. The EZVIZ DL05 panel, as an example, is 360 mm tall and 67 mm wide. Other models are in the same ballpark.

Measure the flat area around the handle on both faces. You need clear flat surface for the full panel height and width, centred roughly on the handle. Look for:

• raised mouldings or carved panels on villa doors in Arabian Ranches, Jumeirah and Al Barsha
• a door viewer (peephole) that’s too close to the handle
• a kick plate, a glass panel or a decorative stud strip running through the panel area
• an architrave or a wall on the hinge side that the inside panel would hit when the door opens fully

Carved timber main doors are the ones that catch people out. The door is thick and solid, so everyone assumes it’ll take anything. Then the panel lands half on a moulding and rocks.

5. Frame gap

Close the door and look at the gap between the door edge and the frame, at the height of the latch. Then open it and check the strike plate on the frame lines up with the latch on the door.

A healthy door has a small, even gap top to bottom. If it’s tight at the top and wide at the bottom, the door has dropped on its hinges. Older villas in Mirdif and Jumeirah, and service doors anywhere, do this a lot.

A heavy mechanical handle can hide a dropped door because you lean on it. A smart lock’s motorised bolt can’t. It’ll stall against the strike, drain the batteries trying, and throw an error. The fix is a hinge adjustment, not a different lock, and it’s cheap when it’s done at the same visit.

And the direction: which way does the door open?

Stand outside the door. Note two things: are the hinges on the left or the right, and does the door swing away from you (in) or towards you (out)?

Manufacturers don’t all use the same left-hand and right-hand convention, so don’t translate it yourself. Just tell the seller “hinges on the left, opens inward, viewed from outside”. Most smart locks with a reversible latch can be set either way. Some panels can’t be flipped, which is why the Lockin handing post exists.

What if your door has a euro cylinder?

If you’re looking at a smart cylinder like the Altix CL1X, you’re not replacing the lock body. You’re replacing the cylinder, the part your key goes into. That needs a different measurement.

Take out the cylinder. Undo the long screw on the door edge, turn the key slightly so the cam lines up, and slide it out. Then measure from the centre of the fixing screw hole to each end of the cylinder. You’ll get two numbers, like 35/35 or 40/50. Measure the loose cylinder rather than in the door, and use the screw hole as the reference, not the cam (this guide shows it well).

Our CL1X product page doesn’t publish a length range. So send us those two numbers and the door thickness, and we’ll confirm it before you pay.

What if you don’t want to measure anything?

There’s a route that skips most of this. A retrofit lock, like the SwitchBot Lock Pro, mounts on the inside of the door over your existing thumbturn. It doesn’t touch the lock body, the backset or the outside of the door.

You still need two checks:

1. You need a thumbturn on the inside. If your inside is key-only, a retrofit won’t work.
2. You need flat space around it. The SwitchBot page lists the unit at 120 x 59 x 83.9 mm, so you need roughly that footprint of clear door around the thumbturn.

It’s the easiest option for renters. We also point people to it when the door has something odd going on, like an unusual lock body, and they’d rather not deal with it.

Which photos should you send?

Numbers plus photos answer nearly every fit question without a site visit. Send these six:

1. The door edge, showing the faceplate where the latch comes out, with the tape measure across the thickness.
2. The inside handle, straight on, from about 30 cm.
3. The outside handle, straight on.
4. The whole door from inside, a few steps back, so we can see mouldings and the hinge side.
5. The strike plate on the frame.
6. If you’ve taken the handle off, the bare holes with the tape across from the edge.

Put the tape in the shot wherever you can. A photo with a ruler in it beats a number typed from memory.

What do your numbers tell you?

Prices are our listed prices on the day of writing. Fitting in Abu Dhabi and the other emirates is AED 550 for a mortise lock and AED 450 for a cylinder.

If you want to open the door or send codes when you’re away from it, the Altix G2 gateway adds AED 179.99 for TTLock-based locks like the CL1X.

Worked example: a 2-bedroom apartment in JVC

Here’s how a typical measure-and-buy goes.

1. Thursday, 19:00. The owner takes the inside handle off his main door. Four screws.
2. 19:05. Door thickness 45 mm. Backset 60 mm from the edge to the centre of the spindle hole. Centre distance 68 mm. So it’s a 6068.
3. 19:08. He checks the panel area. Flat door, no mouldings, peephole well above handle height.
4. 19:10. Frame gap is even top to bottom. The latch lines up with the strike.
5. 19:12. Hinges on the right, door opens inward, viewed from the corridor.
6. 19:15. He sends six photos and the numbers on WhatsApp. We confirm the DL05 fits the pocket and the thickness is mid-range.
7. 19:20. We ask one more question. Is it the main entrance in a tower? Yes. So it’s very likely a fire-rated door, and the building will want to approve the change before anything’s fitted. We send him our NOC guide.
8. The following Tuesday. Building management approves. Our technician fits the lock in about an hour, because nothing had to be cut. AED 499 for the lock plus AED 450 for fitting, AED 949 in total.

Most people skip step 7. His numbers all said the lock would fit, but on a tower entrance door the building gets a say as well.

What goes wrong when people measure?

The most common one is measuring the backset to the edge of the handle instead of the centre. You write down 45 or 50 instead of 60 and order the wrong lock body.

Next is trusting “fits most standard doors” on a listing. UAE doors vary too much for that line to mean anything, so ask the seller for the minimum and maximum thickness.

People also measure thickness at the top of the door because it’s easier to reach. Lock rails and steel cores can make the door thicker or thinner at handle height, which is the only place that counts.

Plenty of villa doors have a separate deadbolt with its own key. A smart lock replaces one of the two locks, so decide before the visit what happens to the other one.

A door that’s dropped on its hinges gets missed, and then the lock gets blamed for a hinge problem. And left and right get flipped all the time. Describe the swing in words, from the outside.

A wrong measurement costs money. A wrong lock means a return, a second visit at AED 450 and then the right lock. If someone forces a lock into a pocket it doesn’t fit, you’ve got a door that needs repair as well.

When shouldn’t you buy yet?

Four situations where we’d tell you to hold off.

The main door of a tower apartment needs your building’s approval first. Most of these are fire-rated doorsets, and only approved hardware should go on them. Our NOC guide covers how that works with the big developers.

When you lift the handle and bolts shoot out at the top and bottom, you’ve got a multipoint lock. Don’t swap it for a single-point smart lock, because the door ends up weaker than it was. Send us photos instead.

Renting? Get the landlord’s okay in writing. The CL1X and the SwitchBot are the easiest to put back on move-out, and our rented apartment post covers how to ask.

An uneven frame gap or a door that scrapes needs fixing before any lock goes on. A motorised bolt on a sagged door fails within months.

Buy the lock that fits your door

How can Altix help?

Send us your five numbers, the direction the door opens, and the six photos on WhatsApp. We’ll tell you which route fits, whether anything needs cutting, and whether we need to see the door before quoting.

If a dimension isn’t on our product page, we’ll check it against your photos and say so, rather than guess. Fitting is AED 450 for a mortise lock and AED 350 for a cylinder in Dubai and Sharjah, AED 550 and AED 450 in Abu Dhabi and the other emirates.

FAQ

What measurements do I need for a smart lock?
Door thickness, backset, centre distance between the handle and keyhole, flat panel space on both faces, and the gap between the door and frame. Plus which side the hinges are on and which way the door opens.

What is backset on a door?
The distance from the door edge to the centre of the handle spindle. On many UAE timber and steel doors it’s 60 mm. On aluminium doors it’s usually 25 to 35 mm.

What does 6068 mean?
A lock body with a 60 mm backset and 68 mm between the handle spindle and the keyhole. 5085 means 50 mm and 85 mm. They’re not interchangeable.

How thick are apartment doors in Dubai?
Most we see run 40 to 50 mm. Fire-rated and steel doors can be thicker. Measure yours near the handle, not at the top.

Do I need to take the handle off to measure?
No, but it helps. With the handle off, you can measure to the centre of the spindle hole, which is more accurate.

How do I measure a euro cylinder?
Take it out, then measure from the centre of the fixing screw hole to each end. You’ll get two numbers, like 35/35 or 40/50.

Is there a smart lock that doesn’t need any measurements?
A retrofit lock like the SwitchBot Lock Pro goes over your inside thumbturn and doesn’t touch the lock body. You only need a thumbturn on the inside and flat space around it.

Can Altix check my measurements before I buy?
Yes. Send the numbers and photos on WhatsApp and we’ll confirm the fit before you pay.