The ideal size of your eBook cover art is a height/width ratio of 1.6:1. This means that for every 1,000 pixels in width, the image should be 1,600 pixels in height. To ensure the best quality for your image, particularly on high definition devices, the height of the image should be at least 2,500 pixels. Ideal dimensions for cover files are 2,560 x 1,600 pixels.