Sizes will differ depending on whether you are creating PSD icons and PNG icon.
Size of PSD icon
You should use a grid that is compatible with the target operating system. For your convenience, you can download our icon grid in Adobe photoshop format.
The PSD icon must be editable vector shape in Photoshop with 1024 x 1024 pixels size.
Size of PNG icon
In order to provide sufficient image data for crisp icon rendering and to be usable in as many scenarios as possible, we require 1024 x 1024 pixels squared PNG icon preview image.
Size of PNG mockup image
To promote your app icon on the social networks, please design an nice app icon preview image with 1200 x 630 pixels size. You should download this icon mockup image template.
You can use this template to design a nice app icon promotion image which helps you increase the sales, this's an example: