How to calibrate

Calibration helps Screen Ruler match your device screen.

  1. Open the app and go to Settings.
  2. Tap Calibration.
  3. Place an object with a known length on the screen.
  4. Drag the scale until it matches the real length.
  5. Save your calibration.

You can reset calibration in Settings at any time.

Calibration FAQ

How accurate is it?

Even before calibration, Screen Ruler adapts the scale for known iPhone and iPad device profiles. If you still notice an offset, calibrate with an object of known length to better match your device.

Can I use inches?

Yes. Screen Ruler supports both centimeters and inches.

What does the magnifier do?

It helps align measurement marks with object edges more precisely.