What size is a 6 x 9 KDP paperback cover?

For 300 pages on white paper the spine is 0.6756 in, so the full cover is 12.926 x 9.25 in (0.125 + 6 + 0.6756 + 6 + 0.125 wide, 9 + 0.25 high). At 300 DPI that is 3,878 x 2,775 pixels.

How many pages do I need for text on the spine?

KDP prints spine text only on paperbacks with at least 79 pages (80 if you use Cover Creator), and the text needs 0.0625 in of clearance on each side of the spine.

Does this work for hardcovers?

No. Hardcover case laminate covers add a 0.51 in wrap and 0.4 in hinges, so use KDP's cover calculator and template generator for hardcovers.

KDP paperback cover size and spine width calculator

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A KDP paperback cover is one file: 0.125 in bleed + back cover + spine + front cover + 0.125 in bleed wide, and trim height + 0.25 in tall. Spine width is page count times the paper's thickness: 0.002252 in for white, 0.0025 in for cream, 0.00235 in for groundwood and 0.002347 in for premium color.

Full cover width: -
Full cover height: -
Spine width: -
Pixels at 300 DPI: -

Grey: bleed (trimmed off). Dashed: trim lines. Blue: spine. Keep text 0.125 in inside the trim lines, and leave the lower right of the back cover clear if KDP adds the barcode for you.

How it is calculated

Page count is rounded up to an even number, as KDP prints it.
Spine = pages x thickness per page for the paper you pick.
Width = 0.125 + trim width + spine + trim width + 0.125 in. Height = 0.125 + trim height + 0.125 in.
Pixels are inches x 300, rounded up, since KDP wants 300 DPI or more.

KDP's own pages disagree slightly on standard color paper, so for that ink, and for any final file, generate the template in KDP's cover calculator.

Questions

What size is a 6 x 9 KDP paperback cover?: For 300 pages on white paper the spine is 0.6756 in, so the full cover is 12.926 x 9.25 in (0.125 + 6 + 0.6756 + 6 + 0.125 wide, 9 + 0.25 high). At 300 DPI that is 3,878 x 2,775 pixels.
How many pages do I need for text on the spine?: KDP prints spine text only on paperbacks with at least 79 pages (80 if you use Cover Creator), and the text needs 0.0625 in of clearance on each side of the spine.
Does this work for hardcovers?: No. Hardcover case laminate covers add a 0.51 in wrap and 0.4 in hinges, so use KDP's cover calculator and template generator for hardcovers.

The rules behind it

Sources

Other free tools

Found a wrong number? Tell us. The code is open on GitHub.