What size should images be in an EPUB?

For ordinary reflowable books, roughly 1600 to 2560 pixels on the long edge is a useful compromise between sharpness and file size for a full-width picture. There is no single screen resolution to design for — tablets vary considerably, and readers can zoom images — so treat that range as an optimisation target, bounded by each store's limits and by what the file size costs you.

What is the maximum size of an image inside an Apple Books EPUB?

5.6 million pixels per interior image. That is exactly 2800 by 2000, or 2366 by 2366 square. A photograph from any current camera is several times that and is refused until it is resized. The rule applies to images inside the EPUB, not to the marketing cover, which is submitted separately and wants at least 1400 pixels on its shorter axis.

Why does image size matter on Kindle?

Under the 70 per cent royalty option, Amazon deducts a delivery cost based on the delivered file size — currently $0.15 per megabyte on Amazon.com. A 30 MB ebook therefore carries a $4.50 deduction in the royalty calculation, and because the deduction comes out before the percentage, a $4.99 book with 30 MB of pictures can earn a royalty of roughly $0.34 on an applicable sale. Resizing pictures to a sensible display size removes most of it.

Should ebook images be JPEG or PNG?

Yes — those two remain the safest choices for a portable retail EPUB. JPEG for photographs and continuous tone, PNG for line art, diagrams and transparency. WebP is a core media type of EPUB 3.3, but retailer support is not universal, and AVIF is not an EPUB core image type at all. Kindle documents GIF, BMP, JPEG, PNG and SVG. Convert anything else before you upload.

Does resizing images for the ebook affect the printed book?

Not if the tool keeps one source and generates derivatives. A print image needs the resolution its physical size requires — about 1535 pixels across for a 130 mm figure at 300 dpi, and 1800 × 2700 for a full-page 6 × 9 plate. Those are close to ordinary ebook sizes, so print does not need bigger files; it needs the uncompressed source. The EPUB export can resize and recompress from that source when doing so saves meaningful space.

Image size for an ebook: pixels, file size and what the stores refuse

A photograph from a phone is around 12 million pixels, and almost none of them are needed: the reader’s screen shows a fraction of that, and the rest is stored, downloaded and decoded for nothing. But the reason to care is not only waste — every store polices image size in its own currency, and Kindle’s is money.

What the stores publish

Apple Books refuses any image inside the EPUB over 5.6 million pixels — exactly 2800 by 2000, or 2366 by 2366 square. A camera photograph fails this until it is resized. The rule applies to the images inside the book; the marketing cover is a separate upload, which wants at least 1400 pixels on its shorter axis.

Google Play Books allows 3200 pixels on the longest edge, and accepts GIF, JPEG, PNG and SVG.

Amazon KDP publishes no pixel ceiling for pictures inside the book, but recommends 1600 × 2560 for the cover and charges for size instead. Under the 70 per cent royalty option, a delivery cost is deducted from the royalty base — $0.15 per megabyte on Amazon.com. A 30 MB ebook carries a $4.50 deduction; on a $4.99 book, 70 per cent of what remains is roughly $0.34. The calculation applies to applicable sales under that royalty option, and rates vary by marketplace.

Kobo and Barnes & Noble police the file rather than the image: the ebook must come in under 20 megabytes at Barnes & Noble Press and 100 megabytes at Kobo. The wider ceiling, for reference: KDP takes ebook manuscripts up to 650 MB, Google Play up to 2 GB per file, Apple Books up to 2 GB.

What a screen can show

There is no single screen to design for. Current iPads alone run from the mini’s 2266 × 1488 — about 3.4 million pixels — to the 13-inch iPad Pro’s 2752 × 2064, about 5.7 million. E-ink readers show less. And readers can zoom: Kindle explicitly lets readers enlarge images, which is why Amazon recommends supplying high-resolution pictures rather than screen-sized ones.

So the honest rule is not “anything larger than the screen is wasted” but a target: for ordinary reflowable books, images in the 1600 to 2560 pixel range stay sharp at full width and under reasonable zooming, without carrying data nobody can use. Below 800 pixels a picture starts to look soft on a modern screen. The cover is the exception on the other side: stores show it large on the product page, and Amazon asks for 1600 × 2560 — keep the cover at that size.

Format

JPEG for photographs and paintings: continuous tone, no hard edges. Quality around 85 on the usual scale is a good starting point — Apple itself recommends quality 85 for fixed-layout images — and a fraction of the size. Lower settings suit some photographs; detailed or noisy images may want more.

PNG for diagrams, line art, screenshots and anything with transparency. A photograph saved as PNG is several times the size of the same picture as JPEG, with no visible difference.

WebP and AVIF are smaller than both, but the standards and the stores do not agree on them: WebP is a core media type of EPUB 3.3, while AVIF is not an EPUB core image type. Apple’s interior-image guidance specifies JPEG and PNG; Google lists GIF, JPEG, PNG and SVG; Kindle documents GIF, BMP, JPEG, PNG and SVG. For a portable retail EPUB, convert to JPEG or PNG before uploading.

GIF holds 256 colours. Fine for a small diagram, wrong for anything with a gradient.

Print is different — but not in the way you expect

A picture printed 130 millimetres wide at 300 dots per inch needs about 1535 pixels across, and a full-page plate at 6 by 9 inches needs 1800 × 2700 — which is 4.9 million pixels, under Apple’s 5.6 million cap. So print images are not automatically bigger than ebook images; they often fit the same pixel range. What differs is the export: print wants the source at full resolution and uncompressed, while the EPUB wants a derivative sized to the store’s limits and the delivery fee.

So keep one high-resolution source. The print export retains the resolution the physical size requires; the EPUB export resizes or recompresses when doing so saves meaningful space without costing visible quality. Doing that by hand means two sets of pictures to keep in step. In Nueel, the export screen’s Pictures setting does it, holding each picture under the limit of the store you picked; see exporting.

Before you upload

Check the largest picture’s pixels against the store’s limit — Apple’s 5.6 million is the one that refuses files.
Check the file size against the store’s limit, and — on Kindle — against the delivery cost it becomes.
Open the book on a phone and on a tablet and look at the pictures at full width. Soft is too small; a slow page turn is too large.

Sources

Apple, Interior image requirements, Optimizing images in fixed-layout books and Prepare your book
KDP, Image guidelines for reflowable ebooks, eBook cover image criteria and Digital book pricing page
Google Play Books Partner Center, EPUB files and Upload content and cover files
B&N Press, Maximum file size
Kobo Writing Life, File types and sizes
W3C, EPUB 3.3

Common questions

What size should images be in an EPUB?: For ordinary reflowable books, roughly 1600 to 2560 pixels on the long edge is a useful compromise between sharpness and file size for a full-width picture. There is no single screen resolution to design for — tablets vary considerably, and readers can zoom images — so treat that range as an optimisation target, bounded by each store's limits and by what the file size costs you.
What is the maximum size of an image inside an Apple Books EPUB?: 5.6 million pixels per interior image. That is exactly 2800 by 2000, or 2366 by 2366 square. A photograph from any current camera is several times that and is refused until it is resized. The rule applies to images inside the EPUB, not to the marketing cover, which is submitted separately and wants at least 1400 pixels on its shorter axis.
Why does image size matter on Kindle?: Under the 70 per cent royalty option, Amazon deducts a delivery cost based on the delivered file size — currently $0.15 per megabyte on Amazon.com. A 30 MB ebook therefore carries a $4.50 deduction in the royalty calculation, and because the deduction comes out before the percentage, a $4.99 book with 30 MB of pictures can earn a royalty of roughly $0.34 on an applicable sale. Resizing pictures to a sensible display size removes most of it.
Should ebook images be JPEG or PNG?: Yes — those two remain the safest choices for a portable retail EPUB. JPEG for photographs and continuous tone, PNG for line art, diagrams and transparency. WebP is a core media type of EPUB 3.3, but retailer support is not universal, and AVIF is not an EPUB core image type at all. Kindle documents GIF, BMP, JPEG, PNG and SVG. Convert anything else before you upload.
Does resizing images for the ebook affect the printed book?: Not if the tool keeps one source and generates derivatives. A print image needs the resolution its physical size requires — about 1535 pixels across for a 130 mm figure at 300 dpi, and 1800 × 2700 for a full-page 6 × 9 plate. Those are close to ordinary ebook sizes, so print does not need bigger files; it needs the uncompressed source. The EPUB export can resize and recompress from that source when doing so saves meaningful space.