See
Kindle Formatting:
Quote:
The actual size of the viewable book area on the Kindle 1 screen is 524px × 640px, and the viewable book area on the Kindle 2 screen is 520px × 622px. Any images larger or smaller than that (including those sized 450px × 550px) will be automatically re-sized until the width or height fits the viewable book area.
|
This is for images inside a MOBI/AZW ebook. I think the cover image will be displayed full-screen (i.e. 600x800). There is more good advice about images at the referenced link.