EPUBFILEWhy cover dimensions are more than a pixel count
A cover has both a resolution and a shape. Resolution is the number of pixels in the image; the aspect ratio is the relationship between its width and height. A large image with the wrong ratio can still be cropped, stretched, or framed with blank space. A small image with the right ratio can still look soft when enlarged.
Retailers also use cover art in different places: product pages, search thumbnails, reading apps, and in some cases inside the ebook itself. Their upload rules and preferred shapes can differ, and those specifications can change. Check the destination store's current instructions before final export.
Build the file around its destination
- Choose your retailer or distributor first. Use its current cover requirements for minimum and recommended dimensions, accepted formats, color profile, and file-size limits.
- Set the canvas to the correct ratio. Enter the exact pixel dimensions before placing artwork and typography. Avoid resizing a finished design into a different shape.
- Export a clean, high-quality image. Use the format the store requests. For screen display, check the exported file at thumbnail size and at full size; tiny type and fine details often disappear first.
- Inspect the final export. Confirm the dimensions and ratio after export, then check that no title, author name, or important artwork sits too close to an edge.
One ebook file, one print file
An ebook cover is usually a single front-cover image. A paperback cover is a print-ready spread with a back cover, spine, bleed, and safe areas. Its spine width depends on details such as page count and paper stock, so an ebook image cannot simply be stretched across a paperback template. Create separate files from the beginning and use the printer's template for the print edition.
A cover embedded inside an EPUB is another use case: it may have different practical trade-offs from the retailer's storefront image. Keep an optimized, clearly identified source file so you can make a platform-specific export without repeatedly recompressing the artwork.
Common mistakes to avoid
- Upscaling a small image: increasing pixel dimensions cannot restore details that were never in the source.
- Using one ratio everywhere: a square or print-shaped image may be rejected or cropped by a store that expects a portrait ebook cover.
- Trusting only the upload check: acceptance means the file passed that platform's technical gate; it does not guarantee sharp artwork or readable thumbnail text.
- Mixing units: storefront cover requirements are usually expressed in pixels. DPI alone does not make a low-pixel image sharper on screen.
