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What can Apple's Measure app do — and what can it not do?

The Measure app is a digital tape measure and a spirit level: it measures distances, heights and rectangles. It cannot create a floor plan, calculate square metres, or save a room.

What the Measure app is

The Measure app ships with iOS and is simply called Measure. It uses the camera and the phone's motion sensors to work out where the room is, and lets you place a starting point and an end point in the air. The distance between them is shown in centimetres or metres.

If you have deleted the app, you can download it again for free from the App Store — it is Apple's own. On iPhone models with LiDAR (iPhone 12 Pro and newer Pro models) it is noticeably faster at finding its footing, because the phone measures the distance instead of calculating it from the image.

The four things the Measure app can actually do

1. Measure a distance between two points

Point the phone at the surface until the white dot appears, tap the plus button to set the starting point, move the phone to the end point and tap again. You can chain several measurements in a row, so you can measure around a door frame without starting over.

2. Measure a rectangle automatically

Point the Measure app at something rectangular — a table, a picture, a door, a screen — and it will often recognise the edges itself and lay down a frame with both width and height at once. It works best when the whole rectangle is within the frame and there is clear contrast against the background.

3. Measure a person's height

Point the camera at a person standing fully within the frame from feet to head, and the app writes the height next to their head. This feature requires LiDAR and is therefore only available on the Pro models from iPhone 12 Pro onwards, and on iPad Pro from 2020 onwards.

4. Act as a spirit level

At the bottom of the Measure app there is a tab with a spirit level. Lay the phone flat on a surface and it shows the tilt in degrees; hold it upright against a door frame and it shows whether the frame is plumb. It is the same spirit level that used to live in the Compass app.

The five things the Measure app cannot do

• It does not create a floor plan. The measurements are left as loose lines in the air. No layout comes out of it.
• It does not calculate areas. If you measure 4.20 m and 3.10 m, you have to multiply them together into 13.02 m² yourself — the app will not do it for you.
• It does not save a room. Close the app or walk out of the room, and the measurements are gone. You can take a screenshot, and that is also what most people end up doing.
• It does not export a file. No PDF, no DXF, nothing you can send to a contractor other than a photo.
• It does not know walls, doors and windows as things. It sees surfaces and edges, not building elements. It therefore also cannot tell you how thick a wall is.

How accurate is the Measure app?

Apple does not publish an accuracy figure, and neither should you assume one. The measurement is good enough to decide whether the sofa fits through the door, but too uncertain to settle a dispute about a home's floor area. What pulls the figure off is worth knowing:

• Poor light and smooth, single-colour surfaces. Without LiDAR the app only has the image to go on, and a plain white wall with no texture gives it almost nothing to lock onto.
• Distance. The further you are from the surface, the less precise the point you place becomes.
• The point you aim at. If you set the starting point on the plaster and the end point on the skirting, you have measured two different things.
• Glass and mirrors. Both fool the camera and the LiDAR alike.

Test it against a known measurement. The fastest way to get a feel for your own phone: measure something whose size you know exactly — a sheet of A4 paper is 21.0 × 29.7 cm — and see how close the app gets. Do it in a bright room and again in a dark one, so you know when you can trust it.

When the Measure app is enough — and when it is not

The Measure app is enough when you need a single figure: the height to the ceiling, the width of an alcove, whether the bookcase fits between the window and the corner, how wide a TV stand there is room for.

The Measure app is not enough when you need the shape of the room. If you need a quote for flooring, paint or underfloor heating, you need square metres and a drawing with the measurements next to the walls. If you are selling or valuing a home, every room needs to hang together in one layout. If you are moving a wall on paper, the rooms need to sit correctly in relation to each other.

What you use instead

For whole rooms and whole homes there are apps that assemble the measurements into a floor plan. If your iPhone has LiDAR, they can scan the room as you walk; if it does not, some of them can be drawn in instead, so you type in the measurements yourself.

HouseSense is built for that job: the scan becomes a measured floor plan with areas per room, a takeoff for contractor quotes, a 3D model with true sunlight, and reports in PDF. In HouseSense the home can also be drawn with your finger on graph paper if the phone has no LiDAR — and the measurements are entered in whole centimetres as internal measurements, wall to wall, the same way you would measure with a tape measure yourself. Everything lives in your own iCloud; there is neither an account nor a server.

A good pairing

The Measure app and a floor plan app do not rule each other out. A workable routine is to scan or draw the whole home once in a floor plan app, and then use Apple's Measure app along the way for the individual measurements that crop up: the height of a radiator, the depth of a cupboard, the distance from a socket to a corner. What needs to be saved and shared belongs in the drawing. What needs to be used right now, the Measure app handles in ten seconds.

One thing neither the Measure app nor a scanner can do

Neither Apple's Measure app nor any scanner app can tell you whether a wall is load-bearing. They measure where the wall stands — not what it is holding up. That answer needs a building surveyor or an engineer on site.