Looks like the white iPhone 4 is roughly 0.2mm thicker than the black iPhone 4 released 10 month ago -- roughly 9.3mm to 9.5mm. MacRumors had this up earlier today, and I noticed it when my trusty Case Mate Barely There case barely fit on my new white iPhone 4. In fact, it fit like my old black iPhone 4 did back when it had BodyGuardz front and back. It still went in, but it was a much closer, almost too close fit compared to the black iPhone 4.
Apple's iPhone 4 spec page lists only 9.3mm as the depth for the iPhone 4, with no breakdown or difference given for the white iPhone 4. Whether the extra thickness has to do with opacity, a layer of UV protection, or something else is unknown.
I tried out a bunch of different cases and those that were just a tiny bit loose on the black iPhone 4 fit perfectly on the white iPhone 4 (like the CaseMate Chrome) while those that just fit the black iPhone 4 were just a tiny bit too tight (like the aforementioned Barely There). Given manufacturing tolerances, that might vary on a case by case basis as well.
Since the white iPhone 4 has the same antenna as the black iPhone 4, people in low signal areas with big watery man-hands are absolutely still going to want a case of some sort.
Here's what I've had a chance to test so far:
I'll update the list as I test more cases, and if you've tried any on your white iPhone, let us know how they fit for you.
Pictures of our measurements, taken at three points on both sides of a July 2010 black iPhone 4 and April 2011 white iPhone 4, after the break!
UPDATE: Apple's SVP of marketing, Phil Schiller, has denied any difference via a Twitter DM. [9to5Mac]
UPDATE 2: Consumer reports also claims to have measured both iPhone 4 colors and found no difference in thickness. [Consumer Reports]