5.8 inches for the iPhone XS, 6.1 inches for the iPhone XR, and 6.5 inches for the iPhone XS Max. The XR gets a special designation because its screen is LCD (like the iPhone 8) rather than OLED ...
The phone launched alongside the iPhone XS, its smaller but otherwise identical sibling. The following month, Apple released the cheaper iPhone XR, which had the same A12 chip but a lesser display ...