Shapes help to emphasize the importance of some screen elements relative to others.

Guidance at a glance (TL;DR):

  • Use more-rounded corners (higher corner radius) for primary actions and components
  • Use squarer, less-rounded corners (lower corner radius) for low-emphasis elements

Corner radius values

Android for Cars provides a set of corner radius values intended to emphasize the importance of various screen elements relative to others.

Corner radius values
R0 R1 R2 R3 R4
0dp 4dp 8dp 16dp Full

Using rounding for emphasis

Rounded and square-cornered shapes in Android Automotive create a visual hierarchy that draws user attention to higher-emphasis elements. Higher-emphasis elements have corners that are more rounded, with a larger corner radius. Lower-emphasis elements have corners that are less round, with a smaller corner radius.

Examples of all four levels of corner radius
Examples of four levels of corner radius, from lowest (0dp = square) to highest (circular)

0dp — Baseline

Use 0dp (square) corners for baseline elements that don’t need any extra emphasis. Basic layout structures such as toolbars or lists should use 0dp corners. Images should also have 0dp corners, unless they are masked by a rounded container (such as a card) or are in a selected state.

Square corner example
The album covers in the grid at right don’t need any extra emphasis relative to each other or to the other elements shown, so they have 0dp corners (detail shown at left)

8dp — Low emphasis

8dp is the default corner radius for rounded shapes. Use this shape to indicate low-emphasis interactive elements, such as cards and containers.

8dp low emphasis example
The notification card shown here uses the default 8dp corner radius (shown at left), giving it less emphasis than the action buttons on the card (as shown at right), which are more important

16dp — Medium Emphasis

Use a 16dp corner radius for components with medium emphasis, including interactive elements and expandable components.

16dp medium corner example
Here, a 16dp corner radius is used to provide medium emphasis for a bottom sheet, which is temporarily more important than the current content on screen

Circular — High Emphasis

Circular shapes have a greater visual impact against mostly rectilinear shapes. They should be reserved for high-emphasis components, such as FABs, Chips, and widgets.

High emphasis fully-rounded corner example
Fully rounded corners and circular shapes are used here to give maximum emphasis to the FAB at bottom left, the action buttons at top right, the FAB at bottom left