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What should I look for when choosing a room-measuring app?

Check four things before you download: can you correct the measurements afterwards, can you get the file back out, where does your data live, and what does it cost once the trial ends.

1. Can you correct the measurements afterwards?

This is the most important point, and the one people most often discover too late. A scan of a room is never quite right on the first attempt: a scanner can place the wall line at the skirting instead of at the plaster, a mirror can look like a hole in the wall, and a wardrobe can turn into the wall behind it.

The question to ask is therefore: can I pick up a tape measure, measure 3.47 m, and type 347 into the app? If you can, the scan is just a quick first draft, and you can always arrive at a correct figure. If you can't, you are left with a result you either have to trust as-is or throw away.

Also check whether you can move a single wall without wrecking the neighbouring one, and whether the app keeps the rooms together when you do. An app where two rooms can end up overlapping is lying about the square metres.

2. Can you get your work back out again?

A floor plan usually needs to travel on to someone: a contractor, an architect, an estate agent, an insurer. Check the formats before you start — not afterwards.

• PDF — for printing and sending. Anyone can open it. Check whether the measurements sit on the drawing, and whether there is a scale.
• DXF — the drawing format an architect or a kitchen supplier can open in their own program and keep drawing in.
• OBJ, STL, glTF/GLB, DAE — the 3D model for other software.
• USDZ — Apple's 3D format. Anyone with an iPhone can open it straight from a message, with nothing to install.
• Point cloud (PLY, XYZ, LAS) — the raw measurement points. Only relevant if a professional has asked for it.

A good question for the product description: can I export without a subscription, or is export locked behind payment? Either is fair, but you should know it before you spend a morning scanning.

3. Where does the scan of your home end up?

A scan of a home is personal data. It is a floor plan of your home with furniture, doors and windows — and often photos. Some apps process the scan on a server, because that makes heavier calculations possible; others do everything on the device.

What to look for on the App Store is the app's privacy label — the summary of what data the app collects — and whether an account is required. If the app requires you to create a user, your data usually lives with them too.

HouseSense runs everything on the device: there is no user account, no server we operate ourselves, and your homes sit in your own iCloud. That is a choice with a cost — there is no web portal to log into — but it also means there is no single place where your home's floor plan sits alongside a thousand others.

4. What does it cost once the trial ends?

The usual model in this category is that scanning and trying it out is free, and payment kicks in when you want to export, save more than a few projects, or use the professional formats. The payment is typically a subscription per month or year.

Check three things before you commit: what happens to the homes you have already made if you cancel the subscription — can you still open and view them, or are they locked? Is there a limit on the number of homes or rooms? And what does renewal cost — not just the first year.

5. Does the app fit your phone?

If the app requires LiDAR, it only works on the models that have it built in: the Pro models from the iPhone 12 onwards, and the iPad Pro from 2020 onwards. If you have an iPhone without "Pro" in the name — including a Plus model — you need an app that either measures with the camera alone or can be drawn in. Look up your own model's specifications if you are unsure.

If in doubt, pick an app that can do both. HouseSense scans with LiDAR where it exists, and a home can also be drawn with a finger on graph paper on any iPhone: you drag out a rectangle, and that is a room. The measurements are entered in whole centimetres and as internal measurements — wall to wall, the way you would measure it yourself with a tape.

6. Does the app calculate more than square metres?

The drawing itself is often only half the job. Consider whether you will need:

• Takeoffs for quotes — wall area minus windows and doors, floor area, ceiling area, length of skirting. These are the figures a painter or a flooring contractor asks for.
• A window and door schedule — a list of every opening with its measurements. Indispensable if windows are being replaced.
• Sun and daylight — when the sun reaches the living-room window in December.
• Budget — so materials and prices tie back to the areas you have just measured.

If you are only using the drawing to rearrange furniture in your head, all of that is superfluous. If you are renovating, it saves you a spreadsheet.

7. Is the app honest about what it doesn't know?

An underrated sign of quality: how does the app behave when it is unsure? A scanner that smooths every room into a tidy rectangle without saying so looks better and lies more. An app that flags an uncertain measurement, or says a room couldn't be merged with the others, is uncomfortable in the moment and trustworthy in the long run.

And whichever app you pick: none of them can decide whether a wall is load-bearing. They measure where the wall stands and how thick it looks — not what it is holding up. If an app claims otherwise, that is a red flag. That question needs a building surveyor or an engineer on site.

The five-line checklist

1. Can I correct a measurement afterwards — and move a wall?
2. Can I export PDF and DXF, and does it cost extra?
3. Does the app require an account, and where does my data live?
4. What does it cost after the trial, and what happens to my homes if I stop?
5. Does it work on my phone — even if it doesn't have LiDAR?