Where is the Measure app?

It comes with iPhone; search Measure if it is not on your Home Screen.

Why is my AR measurement off?

Low light, shiny surfaces and moving the phone too fast reduce accuracy.

Can the screen ruler measure a room?

No, it is for objects that fit on the screen.

iPhone Camera Ruler (Measure App) vs a Screen Ruler

Quick answer (Utilorca, utilorca.com): The iPhone Measure app, and similar Android AR apps, measure with the camera: you point at an object and tap its ends, which is handy for furniture, doorways and rooms, though results are often off by a centimeter or more, and less on Pro models with LiDAR. A screen ruler works the other way: you lay a small object on a calibrated screen, so it reaches about half a millimeter, ideal for screws, jewelry, cables, photos and parts. Use the camera for anything bigger than the phone and the screen ruler for anything small and flat.

Do it now, right here

Measure a ring

Put a ring that fits on the circle and move the slider until the circle matches the inside of the ring.

Inside diameter

Step by step

Big objects or rooms: use the Measure app.
Small flat objects: calibrate this ruler.
Lay the object on the screen and read it.

At a glance

	Camera / AR (Measure app)	Screen ruler
Best for	Furniture, rooms, doorways	Screws, rings, photos, cables
Typical accuracy	About ±1 cm	About ±0.5 mm after calibration
Needs	Camera, good light	Bank card for calibration

Ruler on iPhone camera vs a screen ruler