KDP Spine Width Chart (Paperback & Hardcover)
Your spine width is a function of two things: page count and paper type. Get it wrong by even a few hundredths of an inch and your spine text drifts onto the front or back cover. This page has the exact formulas KDP uses, plus lookup charts in inches and millimeters.
The paperback spine formula
Multiply your final page count by the thickness of one sheet:
| Interior | Per-page thickness | Example: 300 pages |
|---|---|---|
| Black & white · White paper | 0.002252" | 0.6756" |
| Black & white · Cream paper | 0.0025" | 0.75" |
| Black & white · Groundwood | 0.002347" | 0.7041" |
| Premium color · White paper | 0.002347" | 0.7041" |
| Standard color · White paper | 0.002252" | 0.6756" |
Note that cream paper is noticeably thicker — a 300-page cream book has a spine 0.074" wider than the same book on white paper. If you switch paper type after designing your cover, you must redo the spine.
Paperback spine width chart
Spine width in inches (mm in parentheses). Dashes mark page counts outside that paper's allowed range.
| Pages | White | Cream | Groundwood | Premium color | Standard color |
|---|---|---|---|---|---|
| 50 | 0.1126" (2.9) | 0.125" (3.2) | 0.1174" (3.0) | 0.1174" (3.0) | — |
| 79 | 0.1779" (4.5) | 0.1975" (5.0) | 0.1854" (4.7) | 0.1854" (4.7) | 0.1779" (4.5) |
| 100 | 0.2252" (5.7) | 0.25" (6.4) | 0.2347" (6.0) | 0.2347" (6.0) | 0.2252" (5.7) |
| 150 | 0.3378" (8.6) | 0.375" (9.5) | 0.3521" (8.9) | 0.3521" (8.9) | 0.3378" (8.6) |
| 200 | 0.4504" (11.4) | 0.5" (12.7) | 0.4694" (11.9) | 0.4694" (11.9) | 0.4504" (11.4) |
| 250 | 0.563" (14.3) | 0.625" (15.9) | 0.5868" (14.9) | 0.5868" (14.9) | 0.563" (14.3) |
| 300 | 0.6756" (17.2) | 0.75" (19.0) | 0.7041" (17.9) | 0.7041" (17.9) | 0.6756" (17.2) |
| 350 | 0.7882" (20.0) | 0.875" (22.2) | 0.8215" (20.9) | 0.8215" (20.9) | 0.7882" (20.0) |
| 400 | 0.9008" (22.9) | 1" (25.4) | 0.9388" (23.8) | 0.9388" (23.8) | 0.9008" (22.9) |
| 500 | 1.126" (28.6) | 1.25" (31.8) | 1.1735" (29.8) | 1.1735" (29.8) | 1.126" (28.6) |
| 600 | 1.3512" (34.3) | 1.5" (38.1) | 1.4082" (35.8) | 1.4082" (35.8) | 1.3512" (34.3) |
| 700 | 1.5764" (40.0) | 1.75" (44.4) | 1.6429" (41.7) | 1.6429" (41.7) | — |
The hardcover spine formula
Case-laminate hardcovers are different: the boards add thickness, and thin books get a minimum spine so the case can physically close. The formula is:
spine = 0.189" + max(0.45", pages × per-page thickness)
In practice that means every hardcover under ~200 pages has the same 0.639" spine, and it grows linearly from there.
Hardcover spine width chart
| Pages | White | Cream | Premium color |
|---|---|---|---|
| 75 | 0.639" (16.2) | 0.639" (16.2) | 0.639" (16.2) |
| 150 | 0.639" (16.2) | 0.639" (16.2) | 0.639" (16.2) |
| 200 | 0.6394" (16.2) | 0.689" (17.5) | 0.6584" (16.7) |
| 250 | 0.752" (19.1) | 0.814" (20.7) | 0.7757" (19.7) |
| 300 | 0.8646" (22.0) | 0.939" (23.9) | 0.8931" (22.7) |
| 350 | 0.9772" (24.8) | 1.064" (27.0) | 1.0105" (25.7) |
| 400 | 1.0898" (27.7) | 1.189" (30.2) | 1.1278" (28.6) |
| 450 | 1.2024" (30.5) | 1.314" (33.4) | 1.2452" (31.6) |
| 500 | 1.315" (33.4) | 1.439" (36.6) | 1.3625" (34.6) |
| 550 | 1.4276" (36.3) | 1.564" (39.7) | 1.4799" (37.6) |
Hardcover is available for 75–550 pages (5.5 × 8.5, 6 × 9, 6.14 × 9.21, 7 × 10, and 8.25 × 11 trims). Standard color and groundwood are paperback-only.
Three spine rules that get covers rejected
- No spine text under 79 pages (paperback). The spine is simply too narrow.
- 0.0625" clearance — spine text must sit at least 1/16" away from each spine edge, because binding can shift by that much.
- Cream ≠ white — if you change paper type after the cover is designed, the spine changes. This is the single most common cause of a wrapped-spine reject.