what size should I export my graphics, for use in the example/screenshot section of the app on the app store.
Thanks
You should read the dedicated Apple documentation about the subject that gives every info about the icon sizes
Read this Technical Note too where every icon and artwork sizes are described in detail.
For the screenshots published on the AppStore, simply do a screenshot of your app for this (which will be 640x960px if you make your screenshot from an iPhone with Retina display (iPhone4), and 320x480px for iPhone 3GS or older, etc. Namely the size of the screen in pixels, obviously).
To do those screenshots:
either directly on the device hold the Power+Home buttons together and it will display a small/quick "flash" effect on the screen to tell you the screenshot has been saved in your iPhone library
Or from the Xcode Organizer, after you have plugged the iPhone to your Mac obviously, select the iPhone in the list and in the appropriate section of the organizer, click on the button to generate a screenshot directly from Xcode.
Questions like this are answered in the Developer Guide for iTunes Connect:
https://itunesconnect.apple.com/docs/iTunesConnect_DeveloperGuide.pdf
See pages 13 and 14 for size information.
The best place to look for this currently is on the iTunes Connect Developer Guide under "Adding New Apps":
http://developer.apple.com/library/ios/#documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/8_AddingNewApps/AddingNewApps.html#//apple_ref/doc/uid/TP40011225-CH13-SW42
https://help.apple.com/app-store-connect/#/devd274dd925
6.5 inch (iPhone 12 Pro Max, iPhone 11 Pro Max, iPhone 11, iPhone XS Max, iPhone XR)
1284 x 2778 pixels (portrait)
2778 x 1284 pixels (landscape)
5.8 inch (iPhone 12 Pro, iPhone 12, iPhone 12 mini, iPhone 11 Pro, iPhone XS, iPhone X)
1170 x 2532 pixels (portrait)
2532 x 1170 pixels (landscape)
5.5 inch (iPhone 8 Plus, iPhone 7 Plus, iPhone 6s Plus)
1242 x 2208 pixels (portrait)
2208 x 1242 pixels (landscape)
4.7 inch (iPhone SE (2nd generation), iPhone 8, iPhone 7, iPhone 6s, iPhone 6)
750 x 1334 pixels (portrait)
1334 x 750 pixels (landscape)
4 inch (iPhone SE (1st generation))
640 x 1096 pixels (portrait without status bar)
640 x 1136 pixels (portrait with status bar)
1136 x 600 pixels (landscape without status bar)
1136 x 640 pixels (landscape with status bar)
3.5 inch (iPhone 4s)
640 x 920 pixels (portrait without status bar)
640 x 960 pixels (portrait with status bar)
960 x 600 pixels (landscape (without status bar)
960 x 640 pixels (landscape with status bar)
12.9 inch (iPad Pro (4th generation, 3rd generation))
2048 x 2732 pixels (portrait)
2732 x 2048 pixels (landscape)
12.9 inch (2nd generation iPad Pro)
2048 x 2732 pixels (portrait)
2732 x 2048 pixels (landscape)
11 inch (iPad Pro, 4th generation iPad Air)
1668 x 2388 pixels (portrait)
2388 x 1668 pixels (landscape)
10.5 inch (iPad (8th generation, 7th generation), iPad Pro, iPad Air)
1668 x 2224 pixels (portrait)
2224 x 1668 pixels (landscape)
9.7 inch (iPad, iPad mini)
1536 x 2008 pixels (portrait (without status bar)
1536 x 2048 pixels (portrait with status bar)
2048 x 1496 pixels (landscape without status bar)
2048 x 1536 pixels (landscape with status bar)
Mac
One of the following, with a 16:10 aspect ratio.
1280 x 800 pixels
1440 x 900 pixels
2560 x 1600 pixels
2880 x 1800 pixels
Apple TV
1920 x 1080 pixels
3840 x 2160 pixels
Apple Watch (Series 6, Series 5, Series 4, Series 3, SE)
368 x 448 pixels
Related
I am sure this info is somewhere but I can't find it, and the Apple Developer hotline seems to have no idea what I'm talking about. In the assets library for launch screen in Xcode, there are slots labeled:
iPhone Portrait ---> Retina HD 5.5 & Retina HD 4.7
iOS8
iPhone Portrait ---> 2x & Retina 4
iOS 7, 8
iPhone Portrait ---> 1x, 2x & Retina 4
iOS 5, 6
I had launch screens prepared and I have the sizes for these individual files, but I don't see how their sizes correspond to these Apple labels within Xcode. Moreover, the Apple docs here (https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Appendices/Properties.html#//apple_ref/doc/uid/TP40011225-CH26-SW1 which is what Apple Developer referred me to) just refer to iphone 6 and 6s sizes, which doesn't correspond to the Xcode label organization.
This seems like it should be a 1 minute query. What am I missing and where is this super basic information?
If you select the image "slot" in the asset catalog and show the Attributes inspector (on the right-hand side), it will show (among other things) "Expected Size" for each image. Doing that, it looks like:
iPhone Portrait iOS8 Retina HD 5.5: 1242 x 2208
iPhone Portrait iOS8 Retina HD 4.7: 750 x 1334
In the Attributes inspector, you can also choose which "slots" you want included via a series of checkboxes.
Documentation-wise, see the Icon and Image Sizes section of the iOS Human Interface Guidelines.
Paraphrasing from there:
iPhone 6 Plus: Use a Launch File
iPhone 6: Use a Launch File
iPhone 5: 640 x 1136
iPhone 4s: 640 x 960
iPad (#2x): 1536 x 2048 (portrait), 2048 x 1536 (landscape)
iPad (#1x): 768 x 1024 (portrait), 1024 x 768 (landscape)
Also see the Launch Images section, which says:
Although it’s best to use a launch file for iPhone 6 and iPhone 6 Plus, you can
instead supply static launch images if necessary. If you need to create static
launch images for these devices, use the following sizes:
For iPhone 6:
750 x 1334 (#2x) for portrait
1334 x 750 (#2x) for landscape
For iPhone 6 Plus:
1242 x 2208 (#3x) for portrait
2208 x 1242 (#3x) for landscape
It's worth noting that if you're only supporting iOS 8, you can just use a launch XIB or Storyboard and you don't need to worry about particular images sizes. The Launch Images section has information on that.
My most recent app update (which is iOS 8 only) is using XIB files (one for iPhone, one for iPad) and it works great.
Retina HD 5.5 - 1242x2208
Retina HD 4.7 - 750x1334
Retina HD 5.5 landscape - 2208x1242
2x - 640x960
Retina 4 - 640x1136
1x - 320x480
default 320x568
default#x2 640x1136
iTunes Connect asks me for screen shots before publishing my app for distribution in the app store. I know that the screen shot dimension for iPhone 4 in is 640x1136, but what are the screen shot dimension for the newer iPhone 4.7 in and 5.5 in?
Updated for the new iPhones 11, 11 Pro, 11 Pro Max, X🅁, X🅂, X🅂 Max and X.
Size for iPhone 11 Pro Max with #3x scaling, coordinate space: 414 x 896 points and 1242 x 2688 pixels, 458 ppi, device physical size is 3.06 x 6.22 in or 77.8 x 158.0 mm. 6.5" Super Retina XDR display.
Size for iPhone 11 Pro with #3x scaling, coordinate space: 375 x 812 points and 1125 x 2436 pixels, 458 ppi, device physical size is 2.81 x 5.67 in or 71.4 x 144.0 mm. 5.8" Super Retina XDR display.
Size for iPhone 11 with #2x scaling, coordinate space: 414 x 896 points and 828 x 1792 pixels, 326 ppi, device physical size is 2.98 x 5.94 in or 75.7 x 150.9 mm. 6.1" Liquid Retina HD display.
Size for iPhone X🅂 Max with #3x scaling (Apple name: Super Retina HD 6.5 display"), coordinate space: 414 x 896 points and 1242 x 2688 pixels, 458 ppi, device physical size is 3.05 x 6.20 in or 77.4 x 157.5 mm.
let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X🅂 Max Screen bounds: (0.0, 0.0, 414.0, 896.0), Screen resolution: (0.0, 0.0, 1242.0, 2688.0), scale: 3.0
Size for iPhone X🅁 with #2x scaling (Apple name: Super Retina HD 6.1" display), coordinate space: 414 x 896 points and 828 x 1792 pixels, 326 ppi, device physical size is 2.98 x 5.94 in or 75.7 x 150.9 mm.
let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X🅁 Screen bounds: (0.0, 0.0, 414.0, 896.0), Screen resolution: (0.0, 0.0, 828.0, 1792.0), scale: 2.0
Size for iPhone X🅂 and iPhone X with #3x scaling (Apple name: Super Retina HD 5.8" display), coordinate space: 375 x 812 points and 1125 x 2436 pixels, 458 ppi, device physical size is 2.79 x 5.65 in or 70.9 x 143.6 mm.
let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X🅂 and X Screen bounds: (0.0, 0.0, 375.0, 812.0), Screen resolution: (0.0, 0.0, 1125.0, 2436.0), scale: 3.0
Size for iPhone 8 Plus (6, 6s, 7 and 8 Plus) with #3x scaling (Apple name: Retina HD 5.5), Coordinate space: 414 x 736 points and 1242 x 2208 pixels, 401 ppi, screen physical size is 2.7 x 4.8 in or 68 x 122 mm.
Size for iPhone 8 (6, 6s and iPhone 7) with #2x scaling (Apple name: Retina HD 4.7), Coordinate space: 375 x 667 points and 750 x 1334 pixels, 326 ppi, screen physical size is 2.3 x 4.1 in or 58 x 104 mm.
And iPhone 5 for comparison is 640 x 1136, iPhone 4 640 x 960.
Note: To build Apps that utilize the full screen size of the new phones add LaunchImages in the sizes: 1242 x 2208, 2208 x 1242 and 750 x 1334. The size in simulator will be different before these LaunchImages are added, because older Apps are scaled.
You may find this info useful too, taken from Andy Orsow's article (thank you buddy!) What are the iOS screen sizes?:
The sizes below include the iOS status bar area, so be sure to leave room for that in your designs. See the bottom of this article for status bar information.
Remember, mobile projects can scroll, so the screen heights listed below are simply minimum heights for your designs.
Phones
iPhone 6 Plus
Portrait: 1242 x 2208 (Launch Image: iPhone Portrait iOS8 – Retina HD 5.5)
Landscape: 2208 x 1242 (Phone Landscape iOS8 – Retina HD 5.5)
iPhone 6
Portrait: 750 x 1334 (iPhone Portrait iOS8 – Retina HD 4.7)
Landscape: 1334 x 750
iPhone 5, 5S, 5C
Portrait: 640 x 1136 ("iPhone Portrait iOS5,6 – Retina 4" and "iPhone Portrait iOS7,8 – Retina 4")
Landscape: 1136 x 640
iPhone 4, 4S
Portrait: 640 x 960 (iPhone Portrait iOS5,6 – 2x and iPhone Portrait iOS7,8 – 2x)
Landscape: 960 x 640
iPhone 1, 2, and 3
Portrait: 320 x 480 (iPhone Portrait iOS5,6 – 1x)
Landscape: not supported
Tablets
iPad Air / Retina iPad
Portrait: 1536 x 2048 (iPad Portrait iOS 7-9 - 2x)
Landscape: 2048 x 1536 (iPad Landscape iOS 7-9 - 2x)
iPad Mini
Portrait: 1536 x 2048 (iPad Portrait iOS 7-9 - 2x)
Landscape: 2048 x 1536 (iPad Landscape iOS 7-9 - 2x)
iPad - Non Retina
Portrait: 768 x 1024 (iPad Portrait iOS 7-9 - 1x) iOS 5,6?
Landscape: 1024 x 768 (iPad Landscape iOS 7-9 - 1x) iOS 5,6?
Wearables
Apple Watch
42mm: 312x390px
38mm: 272x340px
Status Bar Info
InVision will overlay a status bar on your designs for you, so including it in your design is up to you. However, you’ll want to make sure you account for the status bar at the top of your screen.
At the top of your design, leave room for:
iPhone 6 Plus: 60px height
iPhone 4–6: 40px height
iPhone - Non retina: 20px height
Retina iPads: 40px height
Non-retina iPads: 20px height
If you don't want to include the status bar in your designs, check the box for “My design starts below the status bar” in your project options.
EDITED: I had to add Launch Images to my app, and I was not able to find info how simulators correspond to Apple's image names in Launch Images assets. I found such info at http://www.ios-developer.net/iphone-ipad-programmer/icons_and_graphics/default-image and added here.
This should be a comment to Mixaz's answer but I don't have the rep for that yet. Interestingly enough, from Full resolution screenshots for Iphone 6 and 6+
I just figured this out. In Settings > Display & Brightness, you have to have the setting of Standard. I had my device set to zoomed. With "Zoomed" you get 640x1136 screen grabs. With "Standard", you get 750x1334. Not obvious to me! – Chris Prince Nov 18 '15 at 5:03
On iPhone 5s using iOS7 (not tested 6) my application has black bars on the left and right sides of the screen reducing the screen size, but is correctly opening fullscreen on every other iOS device I have so far tested. Screenshot below.
I have been searching and have not found any mention of this as a bug, have replicated on two iPhone 5's iOS7 devices though and is definitely a problem.
I'm using Air 3.9.
Has anyone encountered this / know how to fix?
I had to include an extra iOS splash screen
Default-568h#2x.png
There is a full list of images here: http://help.adobe.com/en_US/air/build/WS901d38e593cd1bac1e63e3d129907d2886-8000.html, apparently a few Air apps have been getting rejected because they are missing the new iOS7 size images.
Example images:
Default.png - 320 x 480 - iPhone, standard resolution
Default#2x.png - 640 x 960 - iPhone, high resolution
Default-568h#2x.png - 640 x 1136 - iPhone, high resolution, 16:9 aspect ratio
Default-Portrait.png - 768 x 1004 (AIR 3.3 and earlier) 768 x 1024 (AIR 3.4 and higher) - iPad, portrait orientation
Default-Portrait#2x.png - 1536 x 2008 (AIR 3.3 and earlier) - 1536 x 2048 (AIR 3.4 and higher) - iPad, high resolution, portrait orientation
Default-PortraitUpsideDown.png - 768 x 1004 (AIR 3.3 and earlier)768 x 1024 (AIR 3.4 and higher) - iPad, upside down portrait orientation
Default-PortraitUpsideDown#2x.png - 1536 x 2008 (AIR 3.3 and earlier)1536 x 2048 (AIR 3.4 and higher) - iPad, high resolution, upside down portrait orientation
Default-Landscape.png - 1024 x 768 - iPad, left landscape orientation
Default-LandscapeLeft#2x.png - 2048 x 1536 - iPad, high resolution, left landscape orientation
Default-LandscapeRight.png - 1024 x 768 - iPad, right landscape orientation
Default-LandscapeRight#2x.png - 2048 x 1536 - iPad, high resolution, right landscape orientation
Default-example.png - 320 x 480 - example:// URL on standard iPhone
Default-example#2x.png - 640 x 960 - example:// URL on high-resolution iPhone
Default-example~ipad.png - 768 x 1004 - example:// URL on iPad in portrait orientations
Default-example-Landscape.png - 1024 x 768 - example:// URL on iPad in landscape orientations
I am developing an application using the iOS SDK. I need to know what Default splash screen sizes I need.
2018 Update - Please don't use this info !
I'm leaving the below post for reference purposes.
Please read Apple's documentation Human Interface Guidelines - Launch Screens for details on launch screens and recommendations.
Thanks
Drekka
July 2012 - As this reply is rather old, but stills seems popular. I've written a blog post based on Apple's doco and placed it on my blog. I hope you guys find it useful.
Yes. In iPhone/iPad development the Default.png file is displayed by the device automatically so you don't have to program it which is really useful. I don't have it with me, but you need different PNGs for the iPad with specific names. I googled iPad default png and got this info from the phunkwerks site:
iPad Launch Image Orientations
To deal with various orientation options, a new naming convention has been created for iPad launch images. The screen size of the iPad is 768×1024, notice in the dimensions that follow the height takes into account a 20 pixel status bar.
Filename Dimensions
Default-Portrait.png * — 768w x 1024h
Default-PortraitUpsideDown.png — 768w x 1024h
Default-Landscape.png ** — 1024w x 748h
Default-LandscapeLeft.png — 1024w x 748h
Default-LandscapeRight.png — 1024w x 748h
iPad-Retina–Portrait.png — 1536w x 2048h
iPad-Retina–Landscape.png — 2048w x 1496h
Default.png — Not recommended
*—If you have not specified a Default-PortraitUpsideDown.png file, this file will take precedence.
**—If you have not specified a Default-LandscapeLeft.png or Default-LandscapeRight.png image file, this file will take precedence.
This link to "Apple's Developer Library" is useful, too.
As of July 2013 (iOS 6), this is what we always use:
IPHONE SPLASH
Default.png - 320 x 480
Default#2x.png - 640 x 960
Default-568h#2x.png - 640 x 1096 (with status bar)
Default-568h#2x.png - 640 x 1136 (without status bar)
IPAD SPLASH
iPadImage-Appname-Portrait.png * 768w x 1004h (with status bar)
iPadImage-Appname-Portrait#2x.png * 1536w x 2008h (with status bar)
iPadImage-Appname-Landscape.png ** 1024w x 748h (with status bar)
iPadImage-Appname-Landscape#2x.png ** 2048w x 1496h (with status bar)
iPadImage-Appname-Portrait.png * 768w x 1024h (without status bar)
iPadImage-Appname-Portrait#2x.png * 1536w x 2048h (without status bar)
iPadImage-Appname-Landscape.png ** 1024w x 768h (without status bar)
iPadImage-Appname-Landscape#2x.png ** 2048w x 1536h (without status bar)
ICON
Appname-29.png
Appname-29#2x.png
Appname-50.png
Appname-50#2x.png
Appname-57.png
Appname-57#2x.png
Appname-72.png
Appname-72#2x.png
iTunesArtwork (512px x 512px)
iTunesArtwork#2x (1024px x 1024px)
For iOS7 create launch images in the following sizes:
For iPhone 5 and iPod touch (5th generation):
640 x 1136 pixels
For other iPhone and iPod touch devices:
640 x 960 pixels
320 x 480 pixels (standard resolution)
For iPad portrait:
1536 x 2048 pixels
768 x 1024 pixels (standard resolution)
For iPad landscape:
2048 x 1536 pixels
1024 x 768 pixels (standard resolution)
See iOS 7 Design Resources > iOS Human Interface Guidelines > Launch Images
UPDATE 1
For iPhone 6:
750 x 1334 (#2x) for portrait
1334 x 750 (#2x) for landscape
For iPhone 6 Plus:
1242 x 2208 (#3x) for portrait
2208 x 1242 (#3x) for landscape
UPDATE 2
For iPhone X:
1125 x 2436 (#3x) for portrait
2436 x 1125 (#3x) for landscape
You can make them 1024 x 768. You can also check "Status bar is initially hidden" in the plist file.
Update 2020 - Xcode 11
In Xcode 11, you can provide only one image with 1x, 2x, and 3x scales then set it in LaunchScreen.storyboard to fill up the screen and everything goes well!
For Example: (1242pt x 2688pt #1x)
This is the portrait screen size of iPhone 11 Pro Max which is the large iPhone screen size yet so it will give you high-quality splash screen on all iOS devices.
Update 2019 - iOS 12
I have collected all sizes needed for the splash screen. All u need is to just drag images with these sizes and drop them, Xcode will place each size in the right place.
Good luck.
Sizes :
320×480
640×960
640×1136
750×1334
768×1004
768×1024
828×1792
1024×748
1024×768
1125×2436
1242×2208
1242×2688
1536×2008
1536×2048
1792×828
2048×1496
2048×1536
2208×1242
2436×1125
2688×1242
Note
Count of required images are 26 images
but there are 6 duplicated sizes
so u will find the above sizes are only 20.
Here I can add Resolutions and Display Specifications for iphone 6 & 6+ size:
iPhone 6+ - Asset Resolution (#3x) - Resolution (2208 x 1242)px
iPhone 6 - Asset Resolution (#2x) - Resolution (1334 x 750)px
iPad Air / Retina iPad (1st & 2nd Generation / 3rd & 4th) - Asset Resolution (#2x) - Resolution (2048 x 1536)px
iPad Mini (2nd & 3rd Generation) - Asset Resolution (#2x) - Resolution (2048 x 1536)px
iPhone (6, 5S, 5, 5C, 4S, 4) - App Icon (120x120 px) - AppStore Icon (1024x1024 px) - Spotlight (80x80 px) - Settings (58x58 px)
iPhone (6+) - App Icon (180x180 px) - AppStore Icon (1024x1024 px) - Spotlight (120x120 px) - Settings (87x87 px)
For Xcode 9 and latest devices
Portrait
iPhone 4/4S 640 x 960
iPhone 5/5C/5S iPod touch 5th generation 640 x 1136
iPhone 6/7/8 750 x 1334
iPhone 6/7/8 Plus 1242 x 2208
iPhone X 1125 x 2436
iPad non-retina 768 x 1024
iPad retina 1536 x 2048
Landscape
iPhone 6, 7 and 8 plus 2208 x 1242
iPhone X 2436 x 1125
iPad non-retina 1024 x 768
iPad retina 2048 x 1536
With iOS 7+, static Launch Images are now deprecated.
You should create a custom view that composes slices of images, which sizes to all screens like a normal UIViewController view.
https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/LaunchImages.html
With universal app I had iPad splash screen showing up in simulator but not on device. The iPad would instead show the Default.png splash for the iPhone. The Default-Landscape.png and Default-Portrait.png files existing, so wth? Resolution should be correct since I created the screen captures using Window | Organizer | Screenshots and used 'Save as Default Image' for the iPad, then just renamed it.
Turns out (from my one app anyways) the two iPad screen shots have to be moved to the Resources-iPad directory. Then it all works fine. Seems obvious now, but in case anyone else has lost sleep over this...
-Larry
For Adobe AIR iOS Developers, take note that if your iPad Splash images "shift" or display and scale a second later, it's because there are different dimensions depending on what version of AIR you're using.
Default-Portrait.png:
768 x 1004 (AIR 3.3 and earlier)
768 x 1024 (AIR 3.4 and higher)
Default-Portrait#2x.png:
1536 x 2008 (AIR 3.3 and earlier)
1536 x 2048 (AIR 3.4 and higher)
Reference:
http://help.adobe.com/en_US/air/build/WS901d38e593cd1bac1e63e3d129907d2886-8000.html#WS901d38e593cd1bac58d08f9112e26606ea8-8000
Is there a way in the iPhone SDK to calculate the size (in millimeters) of a single pixel?
Answering the question as asked about the size of pixels:
Pixel size on an iPhone and iPod Touch
The earlier iPhones (pre-iPhone 4) Apple iPhone Technical Specifications said : 480-by-320-pixel resolution at 163 pixels per inch(ppi). About 0.006135 inches per pixel or 0.1558282 mm per pixel.
The first three iPod touch generations stated the same 163 ppi.
The iPhone 4 specs said 960-by-640-pixel resolution at 326 ppi . So pixel width is 1 inch / 326 pixels per inch or about 0.003067 inches per pixel or 0.0779 mm per pixel. You use points, not pixels. Edit: As noted in Olaf's comment, below, pixels are actually addressable, using half-points.
The fourth generation iPod touch (Sept 2010) has
specs the same as the iPhone 4, 960-by-640-pixel resolution at 326 ppi
The iPhone 4S (Oct 2011) is unchanged from the iPhone 4 in terms of resolution.
The iPhone 5 (Sept 2012) specs said 1136-by-640 pixel resolution at 326 ppi. Pixel size is unchanged. Screen diagonal is 4 inches.
The iPhone 5C and iPhone 5S (Sept 2013) have the same resolution, pixel size, and diagonal as the iPhone 5.
The iPhone 6, 4.7 inch, (Sept 2014)
specs are 1334-by-750-pixel resolution,
at 326 pixels per inch (ppi). pixel size is unchanged from 4, 4S, 5 5s.
The iPhone 6 Plus, 5.5 inch, (Sept 2014)
specs are 1920-by-1080-pixel resolution,
at 401 pixels per inch (ppi). pixel size is about 20% smaller. The pixel width is 1 inch / 401 pixels per inch or about 0.002494 inches per pixel or 0.06334 mm per pixel.
Pixel size on an iPad
The iPad 1 and 2 are 9.7 inch (diagonal) display with 1024-by-768-pixel resolution at 132 ppi per the iPad specs. That is about .0075758 inches per pixel or 0.1924 mm per pixel.
The new iPad (March 2012) is a 9.7 inch (diagonal) display with 2048-by-1536-pixel resolution at 264 ppi
per the current iPad specs.
That is about .0037879 inches per pixel or 0.09621 mm per pixel.
The iPad Mini (1st generation - October 2012) is a 7.9 inch (diagonal) display with a 1024-by-768-pixel resolution at 163 ppi per the original iPad mini specs. That is about
.006135 inches per pixel or 0.156 mm per pixel.
The iPad Mini 2 (2nd generation - October 2013) is a 7.9 inch (diagonal) display with a 2048-by-1536-pixel resolution at 326 ppi per the current iPad mini specs. That is about
.0030675 inches per pixel or 0.0779 mm per pixel.
The iPad Air 2 (October 2014) and the iPad Mini 3 (October 2014) have the same resolution, pixel size, and diagonal as the previous versions of those products.
Comparison of the iPad Air, and iPad Air 2, iPad Mini, iPad 2 and iPad3.
You don't need to have the iPhone SDK calculate the size of a single pixel. One option is to determine what you are running on and then select the needed mm size.
The iPhone (up to and including the 4S) / iPod Touch screen sizes, with a 3.5 inch (diagonal) display are NOT exactly 2" x 3". They are a tiny bit smaller than that. The iPhone 5 has a 4 inch (diagonal) display.
What the questioner may actually need: points.
See Removers comment to the previous answer. Coordinates are specified in points, not pixels.
Well, the size of a pixel is a constant. The screen size of a current iPhone or iPod touch 2" x 3" (50.8 mm x 76.2 mm) and the resolution is 320 x 480 pixel.
50.8 / 320 (or 76.2 / 480) => the size of 1 pixel is 0.15875 mm x 0.15875 mm