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1. Follow the setup shown in your installed app version.
2. Use the exact reference length displayed on screen, not a different length.
3. Remove a case if it prevents the reference from touching the screen.
4. Match the brackets to that known physical length.
5. Select Use This Calibration.

No. Screen-scale setup uses a physical size reference only. The app does not use the camera, scan documents, or photograph your objects.

A device or display-configuration change can make the saved scale unsuitable. Recalibrate after changing Display Zoom, moving to a different iPhone, or whenever a known reference no longer matches.

Keep the object flat against the usable screen edge. In Ruler mode, place the origin and end marker at the object’s edges. In Digital Caliper mode, place the left and right jaws at its edges. Use the fine-adjustment controls when needed.

Millimeters, centimeters, decimal inches, and fractional inches rounded to the nearest 1/64 inch.

It keeps the app from rotating while you align an object. Unlock orientation from Settings when you are finished.

Check the result with a physical ruler, remove any case that blocks the screen edge, keep the object flat, align to the highlighted contact points, and compare important results with a known physical reference.

If your introduction includes a free measurement, you may change tools, units, and marker positions before viewing the completed result (Finish Measurement in older versions). Opening the app or viewing the default value does not consume it. Some new users instead see a lifetime offer after the introduction. Existing free-use allowances and verified purchases are preserved.

Select Restore Purchases on the lifetime-access screen or in Settings. Use the Apple Account that made the original purchase. Access to Apple’s App Store may be required.

Check your internet connection and App Store access, then select Try Again. Device purchase restrictions can also prevent a purchase. Restore Purchases remains available.

Purchases are processed by Apple. Review eligibility or start a request at reportaproblem.apple.com.

Calibration and measurement work without an account or developer server. Loading a price, purchasing, and restoring require Apple’s App Store. Previously verified lifetime access remains available offline on that device.

It removes only the saved screen calibration. It does not change your purchase, preferred unit, or free-measurement status.