The Kindle eBook Cover size (1600×2560px)
Amazon KDP recommends Kindle eBook covers at a 1.6:1 height-to-width ratio, and 1600x2560 pixels is the ideal size that meets it, sitting comfortably within KDP's accepted range of roughly 1000 up to 10000 pixels on the longest side. This 5:8 portrait shape is the digital equivalent of a printed book cover, and matching it exactly means your cover displays correctly in the Kindle Store, in the reading app, and on the device without letterboxing or distortion.
The cover is doing sales work at a very small scale. In Kindle Store search results and on the recommendations carousel, your cover is often a tiny thumbnail, so the title and author name must be large and legible at that size, not just when viewed full screen. A 1600x2560 file has enough resolution to look crisp on high-density tablet and phone screens while keeping the file efficient, and bold typography with strong contrast is what makes a cover stand out in a wall of competing thumbnails.
KDP also has minimum quality and content requirements for covers, and low-resolution or off-ratio images can be rejected or look poor across devices, so hitting 1600x2560 protects your listing. Keep the title well inside the frame with margins so nothing is clipped at different display sizes. Everything here resizes 100% in your browser with no upload and for free, so your cover art stays private on your device. KDP updates its cover specifications and requirements over time, so verify the current guidelines before publishing your book.