8.5 x 8.5 Book on KDP: Size, Spine Width and Print Cost (UK)

Last reviewed by Robert Prime, 12 October 2026. Checked against Amazon’s own help pages: trim size, bleed and margins, paperback printing cost, paperback royalty and create a paperback cover. Quick Answer: 8.5 x 8.5 inches (21.59 x 21.59 cm) is a square KDP paperback size.