Book cover dimensions, start to finish
The most common mistake in cover setup happens before any designing does: treating the cover as three pictures. It isn't. It is one.
One sheet, wrapped around the book
Your printer prints a single flat rectangle, wraps it around the book block, and trims the edges. Read left to right, that rectangle is back cover, spine, front cover. The front is the right-hand portion of a file, not a file of its own.
So you can't design a front at one size, a back at another, and hope they meet in the middle. Every dimension is measured outward from the trim size in one continuous piece.
Trim size is the finished page
Trim is the size of a page in the printed book: 6 × 9 inches, 5.5 × 8.5, 5 × 8. It is the number the whole cover is built from, and the one to settle first — see Choosing a trim size.
Trim is not the size of your cover file. The file is bigger in both directions, for two different reasons.
Bleed: the eighth of an inch that gets cut off
Paper moves. The cover is printed on a sheet larger than the book and then cut down, and the cut wanders slightly on every copy — by enough to see.
Bleed is the insurance against that. You extend the artwork 0.125 inches (⅛ inch, about 3 mm) past the finished edge on every outside edge: top, bottom, and the two outer sides. That strip is thrown away in the trimming. All four printers we support — KDP, IngramSpark, Lulu and B&N Press — use the same 0.125 inches.
There is no bleed at the spine folds. Nothing is cut there, so bleed exists only where the blade goes.
Safe area: where type is allowed to live
The same wander that eats your bleed can eat your title. The safe area is the inset region where text and anything else you care about has to stay.
- About 0.25 inches in from every trimmed edge. Not the title, not the author name, not a face you'd notice losing a slice of.
- About ⅛ inch clear of each spine fold. The fold moves too, and type that crowds it ends up creeping onto the wrong face.
- Barcode area on the back. Leave the lower right of the back cover clear of anything that matters, whether or not you supply your own barcode.
The arithmetic
Two lines, and they are all of it:
Total width = (trim width × 2) + spine width + (bleed × 2) Total height = trim height + (bleed × 2)
Worked through for a 300-page 6 × 9 paperback on white paper at KDP, whose spine works out to 0.6756 inches — see How to calculate spine width:
- Width: 6 + 6 + 0.6756 + 0.25 = 12.9256 inches
- Height: 9 + 0.25 = 9.25 inches
At 300 dpi, that is 3,878 × 2,775 pixels. Only the spine term is variable: change the page count and the file width changes with it, which is why the page count has to be final before the cover is.
In the Cover Maker. Trim, bleed, safe area and both spine folds are drawn as live guides over your artwork at your real trim size and page count, and the wrap is built to the printer's own measurements rather than a number you typed in. Start a book → · about the Cover Maker
What a wrong wrap looks like
You rarely get a warning. You get a proof, or worse, a copy.
- A white sliver along one edge. The artwork stopped at the trim line instead of running past it.
- Type sliced at the edge. Something sat outside the safe area and the cut took part of it.
- The title bent around the fold. The spine was too narrow or too wide, so the front artwork starts in the wrong place and the wrap slides.
- An off-center front. Same cause. A spine error of a tenth of an inch moves everything to the right of it by a tenth of an inch.
The pattern is worth noticing: a spine mistake is not a spine problem. It is a whole-cover problem, because every measurement to the right of the spine depends on it.
A hardcover is not a paperback wrap
You can't reuse a paperback file for a hardcover. A case-laminate cover is wrapped around boards that are slightly larger than the pages, and the material folds over to the inside of the case, so the printed sheet is meaningfully bigger than trim plus bleed in both directions. The spine is thicker too, because the boards and the hinge add to the paper bulk.
A dust jacket is different again: the same wrap, plus two flaps that fold inside the covers, each one an extra panel of artwork to fill.
None of this is a resize. It is a different sheet, cut differently, and the front artwork sits at a different place on it.
Ebook covers are a simpler thing entirely
An ebook cover is a flat front. No spine, no bleed, no trim, nothing to wrap. It is a tall image — most stores want roughly 1,600 × 2,560 pixels — and the only real constraint is that it still reads at the size a store actually shows it, which is the thumbnail test.
If you're doing both, design the print wrap first and take the front from it. Going the other way means inventing a back cover and a spine after the fact.
Make yours
Everything here is built into the tools, and they are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next: How to calculate spine width · More: Bleed and safe area, explained once · Choosing a trim size · Where to print