An icon is a graphic that takes up a small portion of screen real estate and provides a quick, intuitive representation of an action, a status, or an app.
When you design icons for your app, it’s important to keep in mind that your app may be installed on a variety of devices that offer a range of pixel densities, as mentioned in Devices and Displays. But you can make your icons look great on all devices by providing each icon in multiple sizes. When your app runs, Android checks the characteristics of the device screen and loads the appropriate density-specific assets for your app.
Because you will deliver each icon in multiple sizes to support different densities, the design guidelines below refer to the icon dimensions in dp units, which are based on the pixel dimensions of a medium-density (MDPI) screen.
So, to create an icon for different densities, you should follow the 2:3:4:6:8 scaling ratio between the five primary densities (medium, high, x-high, xx-high, and xxx-high respectively). For example, consider that the size for a launcher icon is specified to be 48×48 dp. This means the baseline (MDPI) asset is 48×48 px, and the high density (HDPI) asset should be 1.5x the baseline at 72×72 px, and the x-high density (XHDPI) asset should be 2x the baseline at 96×96 px, and so on.
Note: Android also supports low-density (LDPI) screens, but you normally don’t need to create custom assets at this size because Android effectively down-scales your HDPI assets by 1/2 to match the expected size.