They aren't accurate, either; the SGS is shown as relatively larger than it actually is (not much, but when making comparisons like this, percentage points matter), and the SGS's "thumb circle" is smaller!

I guess the moral of the story is that if you have 2-inch range of motion with your thumb, you shouldn't get anything larger than an iPhone and probably can't draw consistent diagrams.

Nice catch - not only is the thumb-circle several pixels thinner, it's also clearly shorter top-to-bottom. Good old selection bias at work!

There is no perfect size any more than there is a perfect sized glove, shirt, chair, etc. We programmers have gotten away with ignoring anthropometric variation till now.

Agreed, I have large hands I typically wear xl gloves, and I wish the iphone was larger. Some people may not have large hands but long fingers, there are many variations.

I drew the diagrams from my perspective, holding the phone in my palm, and extending my thumb over the screen. I don't think I have particularly large or small hands. If you hold the phone further out in your fingers, you can extend your thumb farther, but the phone is less stable in your hand. The instability is where the "annoyance" comes from, when I'm using the Galaxy S II.

Do you have elf hands? I've got pretty small hands (I wear a small or medium in men's gloves depending on the brand), and with the iPhone tucked into my thumb as close as reasonably possible, I can reach every pixel on the screen, and I can reach past in spots. If I hold the phone so that it's most comfortable (and most secure feeling), I can reach way past the edge and slightly past the far corners.

Possibly more interesting is where you've put the centre of the arc, half way up the left hand side. As I hold mine, the centre would be over the bottom right corner of the screen, and at "maximum extension" my thumb is just over the top left corner. (I've got "Nash equilibrium" in the back of my head writing this... if I couldn't reach the whole screen, I'd probably change the way I hold my phone.)

I have pretty small hands, but I can hold my 4.2" Xperia Arc phone in a stable way and reach the opposite corner with my thumb.

I think his diagrams are misleading because, as far as I can make out, they are based on a particularly small hand size (perhaps a 9 year old child?). By rotating my thumb, and adjusting the angle I hold the device with my fingers, I reckon I can cope with approximately a 6" diagonal screen, and I don't have big hands. For example, I wear small-size male motorcycle gloves, and most of them are still slightly too long in the finger and glove; my girlfriend wears small size female gloves, and they are only slightly too snug for me. On the basis that glove manufacturers have an economic incentive to know the size distribution of their customers' hands, I think it's implausible to say that anything bigger than 3.5" is too big.

I can reach all the way around the far edge of the device, holding it as I normally do. Perhaps what you are missing is the way I hold my device.

I hold my device resting on my fingers, not gripped in my hand. The first knuckle joint (i.e. the one closest to the fingernail) of my index and pinky fingers are aligned with the center line of the back of the device; the device is balanced on top of my fingers. This gives me the biggest range of movement over the surface of the device, and more importantly gives me better fine control over what my thumb hits - not only is thumb movement a factor, but fine finger movement as well. Adjusting the angle of holding the phone doesn't mean "shifting the device around in my hand" - it merely means changing the angle of my fingers.

I think a bigger factor in how the iPhone is better designed than most other phones is how touchscreen sensitivity drops off around the edges (if this behaviour is indeed deliberate). Before I moved to Android, I used to hold my device gripped between my fingertips and the center of my palm, but I found this didn't work as well with the Nexus One, because the sensitive edge of the touchscreen meant that the little fold of skin from my palm was creating phantom touches on the screen edge. So I stopped gripping my devices; I now hold them all resting on my fingers when I'm using the touchscreen.

"The diagrams drawn are highly misleading - my thumb goes well over the edge of a 3.7" device, and afaik I have pretty normal sized thumbs."

For a man? For a woman? For an American? For an Asian?

Ever considered those differences?

I was refuting his anecdotal claim with mine - I meant this to illustrate the futility of using anecdotal evidence, but the words didn't convey the sentiment as well as I intended.

I fully understand there is most likely some of normal distribution of sizes, but that's a fact that the author seems to have largely ignored as well.

On an unrelated note, the site seems to be down.

Here is some data to help someone answer such questions: http://dined.io.tudelft.nl/en,dined2003,102. It shows that, for Dutchmen, the difference in _average_ hand length between males and females is about 2cm. Looking at the standard deviation and across ages, one gets (at one sd) a variation between long male and short female hands of (I guesstimate) about 5cm. Thumb reach distance will be, say, about half that. I would guess elderly users not only have shorter hands, but also have less dexterity, and of course there are plenty of people outside of the +/- one stadard deviation range (37%, IIRC), so it would not surprise me at all to see difference in 'reach' of over an inch, even in small grouos of users.

And to add to this: it may be acceptable for Apple that 10% of people can't use the device optimally, but it certainly won't be acceptable if 50% of people can't use the device optimally. So you have to err on the smaller side of caution.