Different operating systems have different standard icon sizes. Here's a summary, clicking an operating system you'll scroll down the page to the detailed information with explanations about when to use each of the icon sizes.

Windows 16x16, 24x24, 32x32, 48x48, 256x256
Mac OS X 16x16, 32x32, 64x64, 128x128, 256x256, 512x512, 1024x1024
Linux 16x16, 24x24, 48x48, and 96x96
iOS 6 29x29, 50x50, 57x57, 58x58, 72x72, 100x100, 114x114, 144x144, 1024x1024
iOS 8 29x29, 40x40, 58x58, 60x60, 76x76, 80x80, 120x120, 152x152, 180x180, 1024x1024
Android L 24x24, 48x48, 192x192, 512x512
Windows Phone 62x62, 99x99, 173x173, 200x200
 

Icon sizes for Windows Vista, Windows 7 and Windows 8

Application Icons and Control Panel Items

The icons should be in .ico file format.
The full set should includes following icon sizes:

  • 16x16
  • 32x32
  • 48x48
  • 256x256

Icons for Windows 8 (Metro Design)

  • Application icons 30х30, 50x50, 150x150
  • App Bar icons 26х26
By the way, we make the largest free icon pack of Windows 8 icons. Either download all icons in a single ZIP file or search icons by tags and download only selected ones. Alternatively, you could search our Windows 8 icons on IconArchive, a great site for free icons.

Toolbar Icons

Required sizes: 16x16, 24x24, 32x32.
Note that toolbar icons are always flat, not 3D, even at the 32x32 size.

Dialogs and wizards

Required sizes: 32x32 and 48x48

 

Icon sizes for Mac OS X

Application Icons

To ensure that your app icon looks great in all the places that users see it, you need to provide resources in the sizes listed below:

  • 1024x1024
  • 512x512
  • 256x256
  • 128x128
  • 64x64
  • 32x32
  • 16x16

Toolbars

Create icons for standard- and high-resolution displays. You need to supply two resources:

  • 32x32
  • 32x32@2x (64x64)

Use the PNG format.

Sidebars

Create your icons in three sizes:

  • 16x16
  • 18x18
  • 32x32 pixels (if using PDF)
If you create your sidebar icons in PDF format (recommended), OS X will automatically scale your icon for high-resolution display. You do not need to provide high-resolution versions. However, if you use PNG format for your icons, you will need to supply the following resources:
  • 16x16
  • 16x16@2x
  • 18x18
  • 18x18@2x
  • 32x32
  • 32x32@2x
 

Icon sizes for Linux

Here are the icon sizes from the GNOME specification.

GNOME uses a soft, three-dimensional look. This style is achieved by using antialiasing, shading and highlighting techniques.

Bold denotes the primary size for this kind of icon.

Object and document  
 24x24, 48x48, and 96x96  
Application
 24x24, 48x48  
Toolbar 24x24, 48x48  
Menu 16x16
  
 

iOS 6

iPhone and iPod Touch

iPhone and iPod Touch

Description Standard Resolution High Resolution (Retina Display)
Home Screen Icon 57x57 114x114
Settings Icon 29x29 58x58
Spotlight Icon 29x29 58x58
App icon for the App Stores 1024x1024 1024x1024

iPad

Description Standard Resolution High Resolution (Retina Display)
Home Screen Icon 72x72 144x144
Settings Icon 29x29 58x58
Spotlight Icon 100x100 50x50
App icon for the App Stores 512x512 1024x1024

 

iOS 8

iPhone

Description iPhone 6 Plus (@3x) iPhone 6 and iPhone 5 (@2x) iPhone 4s (@2x)
App icon (required for all apps) 180x180 120x120 120x120
App icon for the App Store (required for all apps) 1024x1024 1024x1024 1024x1024
Spotlight search results icon (recommended) 120x120 80x80 80x80
Settings icon (recommended) 87x87 58x58 58x58
Toolbar and navigation bar icon(optional) About 66x66 About 44x44 About 44x44
Tab bar icon (optional) About 75x75 About 50x50 About 50x50

iPad

Description iPad and iPad mini (@2x) iPad 2 and iPad mini (@1x)
App icon (required for all apps) 152x152 76x76
App icon for the App Store (required for all apps) 1024x1024 1024x1024
Spotlight search results icon (recommended) 80x80 40x40
Settings icon (recommended) 58x58 29x29
Toolbar and navigation bar icon(optional) About 44x44 About 22x22
Tab bar icon (optional) About 50x50 About 25x25

 

Android L

Product Icons

Product icons are the visual expression of a brand’s products, services, and tools. Simple, bold, and friendly, they communicate the core idea and intent of a product. While each product icon is visually distinct, all product icons for a given brand should be unified through concept and execution.

Product icons are an essential vehicle for communicating your brand. Using these guidelines as a starting point, make sure your product icon colors and other key elements reflect your brand identity.

gmail icon

Product Icon Grid

The product icon grid has been developed to facilitate consistency and establish a clear set of rules for the positioning of graphic elements. This standardization results in a flexible but coherent system.

Android L Product Icon Grid

Keyline Shapes

square
circle
 
Vertical Rectangle
Horizontal Rectangle

DP Unit Grid

Device launchers display product icons at 48dp. When you create the icon, maintain the 48-unit measure, but scale it to 400% at 192 x 192 px.

By maintaining the unit ratio, you preserve sharp edges and correct alignment when the scale is reduced.

Product Icon grid 4 to 1

System Icons

A system icon, or UI icon, symbolizes a command, file, device, or directory. System icons are also used to represent common actions like trash, print, and save.

Within the 24dp bounding box, square icons are 18x18dp, circles are 20dp, and rectangles are 20dp on their longest side.

System Icon Grid
 

Windows Phone

Application Iconography

Required Icons in the XAP Package Size
Application Icon 62x62
Application Tile Image 173x173

Windows Phone Marketplace Iconography

Icon Size
Device application icon for Windows Phone Marketplace catalog (small) 99x99
Device application icon for Windows Phone Marketplace catalog (large) 173x173
Desktop application icon for Windows Phone Marketplace catalog 200x200