Book Spine Width Calculator
Enter your page count and paper and this works out the spine width in millimetres and inches — and then the thing you actually need next, which is the full cover artwork size including both boards, the spine and the bleed. Every paper and binding option below is one Printster actually stocks.
What the numbers mean
The spine width is the thickness of the stacked text block plus whatever the binding adds. The cover artwork size is what your designer or your PDF export actually needs: back cover, spine and front cover laid out as one flat sheet, with bleed added on all four edges so the trim can wander a millimetre without showing white.
Spine width is calculated as (page count ÷ 2) × sheet thickness + binding allowance. Sheet thickness comes from the paper’s grammage and its bulk: thickness in mm = gsm × bulk ÷ 1000, with bulk taken as 1.25 cm³/g for uncoated stock and 0.94 for coated matte. That is why 130 gsm matte comes out barely thicker than 100 gsm bond — coating compresses the fibres, so a heavier coated sheet can be thinner than a lighter uncoated one.
Spine width by page count — the papers we stock
Soft cover binding, spine in millimetres. Use this if you just want the number without filling in the form.
| Pages | 75 gsm Normal | 85 gsm Bond | 100 gsm Bond | 130 gsm Matte |
|---|---|---|---|---|
| 32 pages | 2.1 mm | 2.3 mm | 2.6 mm | 2.6 mm |
| 60 pages | 3.4 mm | 3.8 mm | 4.3 mm | 4.3 mm |
| 100 pages | 5.3 mm | 5.9 mm | 6.8 mm | 6.7 mm |
| 150 pages | 7.6 mm | 8.6 mm | 10.0 mm | 9.8 mm |
| 200 pages | 10.0 mm | 11.2 mm | 13.1 mm | 12.8 mm |
| 300 pages | 14.7 mm | 16.5 mm | 19.4 mm | 18.9 mm |
| 400 pages | 19.4 mm | 21.9 mm | 25.6 mm | 25.0 mm |
| 500 pages | 24.0 mm | 27.2 mm | 31.9 mm | 31.1 mm |
What each binding adds
- Soft cover / perfect binding — The cover wraps the glued block, adding about 0.6 mm. Minimum 32 pages.
- Hard binding — Two greyboards and the case material add roughly 4 mm. Minimum 32 pages.
- Hard binding, golden print on front — Same case as hard binding; the foil is on the front board. Minimum 32 pages.
- Hard binding, golden print front and spine — The spine is lettered, so it needs enough width to read - about 6 mm, which is roughly 60 pages on 75 gsm. Minimum 60 pages.
- Glue / tape binding — A tape strip over the glued edge adds about 0.4 mm. Minimum 20 pages.
- No binding - loose sheets — Nothing is added; this is the bare text block thickness. Minimum 1 pages.
Prices are per copy and are the same in every city we deliver to. The full list, including spiral at Rs 40, wiro and comb at Rs 45 and the staple options from Rs 2, is on the binding page.
How accurate is this
To about ±5%. Bulk varies between mills and between batches of the same grammage, and no calculator can know which reel your job runs on. That tolerance is invisible on a 200-page book and it matters on a cover with a tight spine design.
If the spine carries text, print one proof copy before committing to a run and measure the spine you get. A single copy is priced from the same rate card as a hundred, and it is the only way to know for certain. On a spine under about 3 mm, do not put text on it at all — there is not enough width for it to sit straight.
Print your book with this spine
Price your book → · All binding options and prices → · Paper sizes → · Book printing →
Frequently asked questions
- How do I calculate book spine width?
- Spine width = (page count divided by 2) x sheet thickness, plus what the binding adds. Sheet thickness in mm is gsm x bulk / 1000, where bulk is about 1.25 for uncoated paper and 0.94 for coated matte. Worked example: 200 pages on 75 gsm Normal is 100 sheets x 0.094 mm = 9.4 mm, plus 0.6 mm for a soft cover, so 10.0 mm.
- What is the spine width for 100 pages?
- On 75 gsm Normal with soft cover binding, 100 pages is 50 sheets x 0.094 mm plus 0.6 mm = about 5.3 mm. On 100 gsm Bond the same book is about 6.8 mm, and hard binding adds roughly 4 mm on top of either.
- What size should my cover artwork be?
- Flat cover width = back cover + spine + front cover + bleed on both outer edges. For a 200-page A5 book on 75 gsm with soft cover binding: (148 x 2) + 10.0 + (3 x 2) = 312 mm wide by 216 mm high. The calculator above gives this for your own book.
- Does paper GSM change the spine width?
- Yes, and not always the way you would expect. Heavier paper is usually thicker, but coating compresses the fibres, so 130 gsm matte comes out at about 0.122 mm a sheet against 0.125 mm for 100 gsm bond - the heavier coated sheet is very slightly thinner.
- What is the minimum page count for perfect binding?
- 32 pages, which is 16 sheets. Below that the glued edge is too thin to hold. If the spine is to be lettered, allow more - about 60 pages on 75 gsm gets you a 6 mm spine, which is roughly the point where spine text becomes legible.
- How much does hard binding add to the spine?
- About 4 mm. Two greyboards and the case material sit outside the text block, so a 300-page book on 75 gsm is a 14.1 mm text block, which is 14.7 mm as a soft cover and 18.1 mm hard bound.
- Is this the same as the Gutenberg spine calculator?
- No. Several tools are called that. This one is calculated for the papers Printster actually stocks - 75 gsm Normal and Premium, 85 gsm Bond and Duo, 100 gsm Bond and Duo, and 130 gsm Matte - and for the bindings we actually offer, at the prices we charge. If you are printing somewhere else, ask them for their bulk figure and use the formula above.
- Which papers can I actually order?
- For the text block: 75 gsm Normal, 75 gsm Premium, 85 gsm Bond, 85 gsm Duo, 100 gsm Bond, 100 gsm Duo and 130 gsm Matte. Covers go up to 300 gsm in matte or glossy. Trim sizes are A5, B5, A4 and A3. Those are the options in the live price calculator, and they are the only ones this tool offers.