What size should I generate my AI cover art?

Ideogram, Midjourney, DALL·E and the rest don't let you type an inch measurement. They ask for an aspect ratio, and give you back whatever pixel size that ratio produces. So there are only two things to get right: pick the ratio closest to your trim, and make sure the result has enough pixels.

The chart

Bigger than the minimum is always fine — the Cover Maker scales down cleanly. Smaller is the problem.

Always upscale

This is the step people miss. A standard Ideogram generation is about 1024 pixels on the short edge, which is roughly 170 DPI on a 6 × 9 book — soft and visibly fuzzy in print. Ideogram's Upscale doubles it, and 2048 px clears the minimum for all four trims above.

So the reliable recipe is: generate → Upscale → download → upload here.

One caution: Upscale crops to the nearest ratio it supports. Since 2:3 and 10:16 are both on that list, generating at one of those means upscaling won't re-crop your art.

Why the minimums are wider than your trim

A 6 × 9 book needs art wider than 6 inches. Two reasons:

• Bleed. Printers trim the stack of covers slightly off-register, so artwork must run past the cut line and get sliced off. Nothing important goes near the edge — see Trim, bleed and safe area.
• The wrap. The art continues around the edge of the cover rather than stopping at the fold.

The Cover Maker handles all of that for you, but it needs about a quarter inch of extra width to work with, which is why the numbers above are a little larger than trim × 300.

The two trims without an exact ratio

5.5 × 8.5 and 5.25 × 8 don't have a matching preset in any of the major AI tools — no generator offers 11:17. Use 2:3 and let the Cover Maker trim the difference: it's about 3% off the width for 5.5 × 8.5 and under 2% for 5.25 × 8.

That trimming happens automatically. Just don't put anything essential — a face, a lone figure, hand-lettering — hard against the left or right edge of the generated image.

How to check you got it right

Upload the image and look at the Front Cover section. It shows the pixel size and the resulting DPI, and warns you if it's too low. Anything at or above 300 DPI is right; the tool also offers a one-click upscale if you're close but under.

A word on text

Don't ask the AI to put your title on the cover. Generators still produce misspelled and malformed lettering, and it's baked into the image where you can't fix it. Generate the artwork alone and add the title, author and series text in the editor, where it stays sharp vector type in the PDF. See How do I make an awesome front cover image?