OS X icons size

Question

What size should an application icon and menu bar icon for OS X be?

I can deal with small resolution displays but what about Retina - does an icon displayed on the men

Answer 1

The maximum size for the app icon should be 1024 x 1024.

And you have to create both regular and retina resolution icons for 16 x 16, 32 x 32, 128 x 128, 256 x 256, 512 x 512 & 1024 x 1024.

The details for which you can find in the "High Resolution Guidelines for OS X" document from Apple.