Book Spine Calculator
Enter your page count, interior type, and trim size to get the exact spine width and full cover dimensions for KDP, Lulu, and IngramSpark.
Full cover = back (6") + spine (0.450") + front (6") + 0.125" bleed on each outer edge. Height = trim (9") + 0.125" top + 0.125" bottom.
How spine width is calculated
Each print platform publishes a pages-per-inch (PPI) factor that depends on paper type. For black-and-white interiors, it's typically 444 PPI (cream or white paper). For color interiors, it's 400 PPI. Divide your page count by the PPI and you get the spine width in inches.
The full cover wraps around: back cover + spine + front cover, plus bleed extending beyond each outer edge. That's what the “cover width” number above gives you — the total width your cover PDF should be.