Amid rumors of a significantly larger "iPhone Math", Instapaper developer Marco Arment has spent time developing some speculation and a few mockups showing how Apple could achieve an iPhone with a nearly 5-inch without disrupting the existing app ecosystem.
The recently rumored, larger-screened “iPhone Math”, or more likely “iPhone Plus”, is plausible as an additional model (not a replacement) alongside the 4” iPhone. And there’s a good chance that it would have a 4.94”, 16:9 screen.
The theory is easy to understand: perform John Gruber’s Mini-predicting math backwards. The iPad Mini uses iPhone 3GS-density screens at iPad resolution. What if an iPhone Plus used Retina iPad screens with iPhone 5 resolution, keeping the rest of the design sized like an iPhone 5?
In the scenario put forth by Arment, an 1136x640 screen matching the iPhone 5's resolution but blown up to the Retina iPad's 264 pixels-per-inch resolution would measure 4.94 inches diagonally.
Left to right: iPhone 5, Galaxy S III, "iPhone Plus", Galaxy Note II
Arment notes that such an iPhone Plus maintaining the same relative proportions as the iPhone 5 but with the larger screen would measure somewhere between the Galaxy S III and the Galaxy Note II, but that Apple would likely be able to trim down the chin and forehead of the device somewhat to bring the device closer to the Galaxy S III's overall size.
At an iPad-like pixel density of 264 ppi, Apple could have a hard time positioning the iPhone Plus as a Retina device given that a phone is assumed to be held closer to the eye than a tablet, but some consumers may still prefer the option of having a larger screen to offer more flexibility such as being able to zoom out further on text or view small text with the device held further from the eye.
Arment offers several other mockups showing what Apple's iOS device lineup would look like with a larger iPhone in it, as well as how users could take advantage of smaller font sizes on the larger screen to show more text.
