Different authors and designers have varying preferences on ebook cover size. While there are no single recommended sizes, studying the topselling books in your genre can help determine the ideal dimension, such as 1.5 for fiction.

I recommend making the original files large (e.g. 3200 x 4800 pixels), then downscaling for different sites. A smaller size of 1600 x 2400 pixels works on all major sites, and the large file can be used for a paperback version. Make sure you use 300 dpi/ppi and do not let the file get too large – Amazon’s limit is 50 MB and some other sites have a smaller limit.

For Amazon KDP, it is best not to go smaller than half of the 3200 x 4800 size. Non-fiction books tend to have a wider size. Different sizes may work, and it is a good idea to study the covers used in your genre and theme. Often Historical Romance covers might be slightly narrower.