iOS icon file resolution

Description	Size for iPhone and iPod touch (in pixels)	Size for iPad (in pixels)	Guidelines
Application icon (required for all apps)	57 x 57 114 x 114 (high resolution)	72 x 72	“Application Icons”
App Store icon (required for all apps)	512 x 512	512 x 512	“Application Icons”
Launch image (required for all apps)	320 x 480 640 x 960 (high resolution)	For portrait: 768 x 1004 For landscape: 1024 x 748	“Launch Images”
Small icon for Spotlight search results and Settings (recommended)	29 x 29 58 x 58 (high resolution)	50 x 50 for Spotlight search results 29 x 29 for Settings	“Small Icons”
Document icon (recommended for custom document types)	22 x 29 44 x 58 (high resolution)	64 x 64 320 x 320	“Document Icons”
Web clip icon (recommended for web apps and websites)	57 x 57 114 x 114 (high resolution)	72 x 72	“Web Clip Icons”
Toolbar and navigation bar icon (optional)	Approximately 20 x 20 Approximately 40 x 40 (high resolution)	Approximately 20 x 20	“Icons for Navigation Bars, Toolbars, and Tab Bars”
Tab bar icon (optional)	Approximately 30 x 30 Approximately 60 x 60 (high resolution)	Approximately 30 x 30	“Icons for Navigation Bars, Toolbars, and Tab Bars”
Newsstand icon for the App Store (required for Newsstand apps)	At least 512 pixels on the longest edge	At least 512 pixels on the longest edge	“Newsstand Icons”

http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/mobilehig/IconsImages/IconsImages.html