Rewritten on the April 14, 2012 Introduction Currently, there's a lot of discussion whether or not Apple should put a bigger screen in the next generation iPhone. This post is not to discuss whether or not if Apple is going to increase the size of the iPhone's display. This post is what size Apple will choose when they increase the size of the iPhone's display. Currently, the iPhone has got a 3.54" display (give or take a few 0.001 inches) with a resolution of 960 by 640 (which gives us a pixel density of 326 pixels per inch). In this post I'm going to describe what I think is the most logical thing to do for Apple when increasing the display's size. Demands - Apple must be able to call it a retina display. Apple really pushes the 'retina display' term and they were willing to even call the iPad 3 a retina display, even though the pixel density is much lower than that of the iPhone 4S. - The same 3:2 aspect ratio The recent idea that Apple might actually only increase the height of the display and keeping the pixels the same size is nice, but it's really unlike Apple. Apple wants to make things easy for developers: it's going to be a 960 by 640 resolution, and if not than it's going to be 1920 by 1280 resolution - nothing in between. - A 960 by 640 resolution, or else a 1920 by 1280 resolution I'm sure that Apple will not choose for some uncommon resolution and that they are going to change the aspect ratio. Apple wants to make things easy for developers and if we look at the iPad 3 they are not going to change that. Apple went for a 2048 by 1536 resolution with the iPad 3: they could have gone with something in between the old and new resolution, but that would mean troubles for the developers. Thus, Apple has shown us that they are not settling with an 'in-between' solution. It's going to be 960 by 640, or in the best-case scenario a 1920 by 1280 resolution (but very unlikely). So, what is Apple going to do according to me? If Apple is going to increase the display size, than they are settling with a 4.37"~ display (give or take a few 0.01 inches). If they keep the same 960 by 640 resolution, it's going to have 264 pixels per inch. And this is why I think they are going to settle with a 4.37 inch display: - Existing infrastructure Think about it: Samsung, Sharp and LG are already producing 264 pixels per inch displays for Apple (for the iPad 3). It will cost little money to also produce smaller displays. Switching pixel density is very expensive. If we look at the list I gave you earlier, than only a 4.37 inch would be the most logical decision for Apple: it saves the most money. It is really expensive to change an existing production line so new displays with different pixel densities can be produced. So: all of Apple's suppliers can produce 264 ppi-displays in huge quantities right now. Switching from pixel density is very expensive and it takes time to switch from pixel density. Bonus example: John Gruber has indicated that Apple is indeed testing 7.85" iPads with a resolution of 1024 by 768 pixels per inch. Let's assume this is correct, than I can tell you why they have choosen for a size of 7.85": A 7.85 inch display with a 1024 by 768 resolution would result in a pixel density of 163 pixels per inch. It just happens to be Apple has already 'set up' a 163-ppi-display-line: they are producing displays with 163 pixels per inch for the iPhone 3GS. Thus, the most logical decision for Apple would be to settle with a new 163 ppi display. - Good size Not only the infrastructure exists, it's also a good size for the coming years. Apple is known for creating amazing designs and they could put a 4.37" display in an iPhone without dramatically increasing the physical dimensions. It's not too small, but it's definitely not too big. - What about the 'retina display'? Well, currently Apple says that the iPhone 4S is a retina display when you hold it 12 inches away from your eye. So now I hear you asking, when is a 4.3" 960 by 640 display 'retina-worthy'? Well, when you hold it at 13 inches from your eye! So, I hear you thinking: "Apple said you can't distinguish the pixels on an iPhone when you hold it 12 inches away (the common holding distance). You must hold a 4.37" iPhone 13 inches away..." That's correct, but Apple could argue that a user holds the iPhone one inch further away because the display is bigger. An iPhone 4.37" 960 by 640 display would be a retina display when you hold it away 13 inches. An iPhone 4S 960 by 640 display is already a retina display when you hold it away 12 inches. And what if they settle with a 1920 by 1280 resolution on a 4.37" display? Well, that would be great. First of all, there won't be a discussion whether or not it will be a retina display. It will definitely be a retina display because than it will have a pixel density of 528 pixels per inch. Second of all, it would allow Apple to introduce a 4K iPad display somewhere in the coming years (the industry will be moving forward to a 4K resolution in the coming years). It is it likely? Nope. So, what if Apple does not settle with this 4.37" display Than that would be simply illogical. It would cost them a lot and production would be slow at first. The smartest move would be to use a display with a pixel density that its suppliers can already produce. But if they don't settle with a 4.37" display, any size could be used. Conclusion The most wise thing to do for Apple is to go for a 4.37" display: the infrastructure is there so almost no problems with supply, it doesn't cost too much money and it's a safe choice for the coming years: not too big, not too small.