How accurate is iPhone LiDAR for room measurements?

Doors, windows and short walls: within a centimeter or two

The clearest public test of the sensor itself comes from a 2024 peer-reviewed study in the HBRC Journal. Researchers scanned a university hall with an iPad Pro and measured the same doors, windows and walls in a model from a Trimble TX8 terrestrial laser scanner, the kind of instrument survey firms use as a reference. They used a general 3D scanning app, not Apple's RoomPlan, so this is a test of the LiDAR hardware.^[1]

One hall, one fast pass with an iPad Pro. Abdel-Majeed et al., HBRC Journal, 2024.^[1] Inch conversions are ours.

What was measured	iPad LiDAR, one moving pass	Laser scanner	Gap
Door width	0.916 m	0.930 m	1.4 cm (0.55 in)
Door height	2.088 m	2.100 m	1.2 cm (0.47 in)
Window width	1.456 m	1.440 m	1.6 cm (0.63 in)
Window height	0.933 m	0.940 m	0.7 cm (0.28 in)
Wall height	2.450 m	2.400 m	5.0 cm (2.0 in)
Wall length	8.555 m	8.850 m	about 29 cm (11.5 in)

The pattern is the whole story. Openings and room-height dimensions land within a centimeter or two. The one long wall, captured while the device kept moving, came out short by almost a foot.

Long walls: where a fast single pass drifts

LiDAR on a phone measures distance to each surface very well. What adds error on long walls is the phone working out where it is while you walk. Small tracking errors add up over distance, which researchers call drift.^[3] The HBRC study shows it clearly, and shows the cure: slow, overlapping capture.

RMSE is the typical error. The slow method was 20 overlapping still scans joined on paper targets. Abdel-Majeed et al., 2024.^[1]

Length measured	One moving pass (RMSE)	Slow overlapping scans (RMSE)
1 m (3.3 ft)	1.9 cm	1.2 cm
2 m (6.6 ft)	3.3 cm	3.3 cm
6 m (19.7 ft)	29.2 cm	2.9 cm
9 m (29.5 ft)	32.1 cm	1.3 cm

The authors put it simply: within 1-2 cm for features up to about 3 meters, and more than 25 cm possible beyond 4 meters in a fast single pass, while the slow method held 1-2 cm at every length.^[1] The sensor's range is about 5 meters, so a scan also has to walk close to every wall.^[1]

What this means for a room scan with RoomPlan

A room-scanning app does not hand you a cloud of raw points. Apple's RoomPlan, which PlaceAnew is built on, combines the camera and the LiDAR readings with trained models to find walls, doors, windows, openings and furniture, and turns them into a clean, measured model.^[4] That changes what accuracy means: the question becomes how well the walls, rooms and openings are placed.

The best answer so far is a 2026 peer-reviewed study of a RoomPlan app against a laser scanner. It found every room in a house and two office floors, matched total wall area within 2%, and drew room areas 5-6% smaller than the laser model.^[3] The full breakdown is in How accurate is Apple RoomPlan?

Our own office test of PlaceAnew lines up with the research: the longest wall, 17 feet 2 inches, came out a third of an inch long, and every wall we could compare landed within 2.5 inches of a hand-measured plan.^[2] See the office test, wall by wall.

How to get the most accurate scan

• Light the room. Apple recommends at least 50 lux, ordinary room lighting with the lights on.^[5]
• Walk calmly and close the loop. Drift comes from fast, long single passes. Sweep each wall from floor to ceiling and come back to where you started.
• Keep each scan within Apple's envelope: a room up to 30 by 30 feet and a single scan under 5 minutes.^[5]
• Watch mirrors and glass. Apple names full-height mirrors and glass as hard for the LiDAR sensor.^[5]
• See what the app filled in. PlaceAnew draws a wall it could not see as dashed and marks anything it estimated, so a measured line and a filled-in one never look the same.

What to do with the scan

Use it for the layout, the design, the client presentation, the estimate and the drawings you send to the shop. Long walls are where a fast pass drifts, which is why the walk is calm and closes the loop. Where PlaceAnew could not see, the plan says so with a dashed wall or an "estimate" label, and Walk replays the visit so you can look at a corner again from the office. See Do I still need a tape measure?

Questions people ask

Is iPhone LiDAR as accurate as a laser distance meter?

For a single point-to-point line, a laser distance meter is more precise. A room is many lines: LiDAR measures every wall, door and window in one walk, so nothing is forgotten, nothing is misread off a notepad and nothing has to be redrawn.

Does it matter which iPhone or iPad I use?

RoomPlan runs on every iPhone and iPad Pro with a LiDAR Scanner. PlaceAnew needs an iPhone 12 Pro or a newer Pro model, or an iPad Pro from 2020 or later.

Has anyone measured PlaceAnew itself?

Yes, in our own office: all 7 wall lengths that compare one to one with a hand-measured plan came within 2.5 inches, median under 1 inch.^[2] See the office test, wall by wall. The published studies on this page tested the LiDAR hardware and another app built on the same Apple RoomPlan technology. Our test method is public too: how to test a room scan app's accuracy.

Does a dark room or a mirror cause errors?

Yes, for every LiDAR app. Turn the lights on and open the blinds. Next to a mirror or a large window, a wall PlaceAnew could not see is drawn dashed, and Walk lets you look at it again from the office.

Next step

Scan one room you know well and see the plan, the 3D model and the PDF report it gives you. For the remodeling view of the same evidence, read Is LiDAR accurate enough for remodeling?