iPhone 15 Pro screen size: 1179 by 2556

Two different pixel counts are in play and confusing them is the usual source of blurry mockups. 1179 by 2556 is the physical resolution of the panel. The layout the browser and the operating system work in is a third of that, 393 by 852, because the display runs at a three times scale factor. Both numbers divide exactly, which is not always the case on this class of device.

That gives a clear working rule. Lay a design out at 393 by 852 in whatever units your tool calls points or CSS pixels, and export raster assets at three times, which lands on 1179 by 2556. Designing directly in device pixels and dividing later leaves you with fractional layout values that round differently in different places.

The ratio is 131:284 after dividing both numbers by their greatest common divisor of nine. That is 1:2.168, considerably taller than the 9:16 that vertical video assumes, so a 1080 by 1920 export shown full screen on this device is either letterboxed or cropped. Full bleed artwork for a phone should be built to the device shape, not to the video shape.

The frame is not a plain rectangle either. The corners are rounded and there is a cutout across the top of the display, so the usable rectangle is smaller than the panel. A mockup that places a headline in the top strip will show it partly behind the cutout on a real device.