Here’s a size guide for Apple Watch icons and menu items.
These are the launch screen and notification icons that represent your application.
Home screen icons are circular and the following table lists the appropriate diameter and usage for each icon. Create your icons as full-bleed square images using the given dimensions. The system applies the circular mask automatically.
Create all of your image resources as
@2x images. There is no need to include non
@2x resources in your Watch app bundle. For all images and icons, the PNG format is recommended. Avoid using interlaced PNGs. The standard bit depth for icons and images is 24 bits—that is, 8 bits each for red, green, and blue. You can include an 8-bit alpha channel but doing so is not required. You can also use PNGs with indexed colors to save space in your image files.
Menus are displayed after a Force Touch is detected and will always apply to the context of the current screen. They are full-screen and can display between 1 and 4 actions, each of which must be composed of an icon and a label. The alpha channel of the image defines the resulting shape. Color information in the image is ignored.
For menu images, the PNG format is recommended. You should avoid using interlaced PNGs.
Hope you find the info helpful!