Prominent Apple blogger, John Gruber did the maths and came up with what he believes is the likely display resolution Apple will adopt for upcoming 4.7-inch and 5.5-inch iPhones.
According to Gruber:
I’ve spent much of the last month trying to figure out the pixel counts for these displays, and it’s actually quite tricky. When Apple changed the iPhone display previously, they did so in obvious ways. With the iPhone 4’s retina display, Apple kept the physical size exactly the same (3.5 inches1) and exactly doubled the pixels-per-inch resolution. When the iPhone 5 increased the size to 4 inches and the aspect ratio (switching from 3:2 to 16:9), they simply added pixels vertically. Same pixels-per-inch resolution, same width (640 pixels), new height (1136 pixels instead of 960).
There is no similar “easy” way to do either a 4.7 or 5.5 iPhone display.
But after giving it much thought, and a lot of tinkering in a spreadsheet, here is what I think Apple is going to do:
4.7-inch display: 1334 × 750, 326 PPI @2x
5.5-inch display: 2208 × 1242, 461 PPI @3x[/su_quote]
Gruber stressed that his theory is based on second hand rumours and past history rather than leaks “from people familiar with the matter.”
Also of note is that John Gruber’s theoretical resolution for the 4.7-inch iPhone display contradicts a recent report from 9t5Mac which suggests that 828 x 1472, 359.34 PPI is the likely resolution of the 4.7-inch iPhone 6. However, the two reports agreed on the 5.5-inch iPhone 6 will likely feature a 2208 × 1242, 461 PPI @3x display.