You may already noticed that most of ruler apps are actually wrong.

Accurate Ruler renders according to screen width spec of the device that your are currently using. So It is accurate.
Already tested in following devices including:
iPhone X, XR, XS, Max
All sizes of iPad 2019
iPhone 4
iPhone 4s
iPhone 5
iPhone 5s
iPhone 5c
iPhone 6
iPhone 6 plus
iPhone 6s
iPhone 6s plus
iPhone se
iPhone 7
iPhone 7 plus
iPad 2
iPad 3
iPad 4
iPad air
iPad air 2
iPad mini
iPad min 2
iPad min 3
iPad mini 4
iPad p​​ro,
iPod Touch 5/6
If your device is one of them, we insure it is accurate.