For the screen dimensions, Apple uses 'points' as a point of reference and maps these points on pixels. As a result, elements have a fixed size regardless of the resolution (i.e. an icon an iPad 2 is just a big as on a retina iPad 3). If we use the 'points' as a frame of reference in stead of actual pixels, there are two different densities (163 PPI and 132 PPI): iPhone (2G, 3G, 3GS, 4, 4S, 5, 5S) - Screen width: 1.96" / 320 points - Density: 320/1.96 = 163 points per inch iPad Mini - Screen width: 4.74" / 768 points - Density: 768/4.74 = 163 points per inch iPad 1/2/3/4 - Screen width: 5.82" / 768 points - Density: 768/5.82 = 132 points per inch To summarize, iOS devices are available with screen sizes that allow for two different physical sizes of elements. My estimate would be that the 132 PPI of the iPad will some day be used for a larger iPhone. Currently, the iPhone 5 has 4" screen with 163 PPI. For a larger phone with 132 PPI, The diagonal then would be: - Current 16:9 diagonal: 4" - New 16:9 diagonal: (163/132)*4 = 4.94" So there you have it, the larger iPhone will be 4.94", thus being 'the inverse' of the iPad mini, which is an iPad with iPhone resolution, while the larger iPhone would be an iPhone with iPad resolution.