Perfect bound books · Artwork guide

Book Spine Sizes: How Wide Should Your Spine Be?

Your pages are designed, the page count is locked, and there's one number standing between you and a print-ready cover: the spine. Find it below in seconds — then use it to size your cover spread and inside pages exactly right.

Calculate my spine size See the full chart

Real production data — from the books we print every weekFree file check on every jobSpine confirmed at proof stage

One cover spread — back cover, spine, front cover — the spine width is the bit that changes with your page count and paper.

Free spine calculator

Your spine size, cover spread and page sizes — in one go

Pick your book size, tell us how many inside pages you have and which paper they're printing on. We'll give you the spine width and the exact dimensions to set up both PDFs.

Book size (height × width)

Height (mm)

Width (mm)

Inside pages

The pages between the covers. Don't count the 4-page cover.

Inside paper

3mmspine width

A5 book · 40 inside pages · 130gsm Silk or Gloss

PDF 1 · Cover spread

210 × 299mm216 × 305mm with 3mm bleed

PDF 2 · Inside pages

210 × 148mm216 × 154mm with 3mm bleed

Your inside pages PDF should contain exactly 40 pages in reading order — no covers.

✅

Every spine is confirmed before we print

Use these figures to set up your artwork with confidence. When your files arrive we check the spine against your actual page count and paper as part of our free file check, so nothing slips through.

The three-second version

Three things decide your spine width

A perfect bound spine is simply the stack of paper inside the cover, so it grows with every page you add and every step up in paper weight. Here's all you need to read the chart.

Count your inside pages

That's every page between the covers. A "4 + 40pp" book has a 4-page cover and 40 inside pages — the 40 is the number you want.

Know your inside paper

130gsm silk, 120gsm uncoated, 170gsm gloss… the weight and finish set how thick each sheet is. Silk and gloss of the same weight share a spine size.

Read off the spine

Find your page count in the chart, run across to your paper, and that's your spine in millimetres. Between two rows? Use the nearest — or the calculator above.

Spine size chart

Spine widths by page count and paper stock

All figures in millimetres, rounded to the nearest whole millimetre, for perfect bound (PUR) books. Only your inside pages count — the spine is set by how many there are and the paper they're on. Silk and gloss of the same weight share a column.

Inside pages	130gsm Silk / Gloss	120gsm Uncoated	150gsm Silk / Gloss	140 / 150gsm Uncoated	170gsm Silk / Gloss	170gsm Uncoated
28pp	2mm	3mm	2mm	3mm	3mm	3mm
32pp	3mm	3mm	3mm	3mm	3mm	4mm
36pp	3mm	3mm	3mm	4mm	3mm	4mm
40pp	3mm	3mm	3mm	4mm	3mm	5mm
44pp	3mm	4mm	3mm	4mm	4mm	5mm
48pp	3mm	4mm	4mm	5mm	4mm	5mm
52pp	4mm	4mm	4mm	5mm	4mm	6mm
56pp	4mm	4mm	4mm	5mm	5mm	6mm
60pp	4mm	5mm	4mm	6mm	5mm	7mm
64pp	4mm	5mm	5mm	6mm	5mm	7mm
68pp	4mm	5mm	5mm	6mm	6mm	7mm
72pp	5mm	6mm	5mm	7mm	6mm	8mm
76pp	5mm	6mm	5mm	7mm	6mm	8mm
80pp	5mm	6mm	6mm	7mm	6mm	8mm
84pp	5mm	6mm	6mm	8mm	7mm	9mm
88pp	5mm	7mm	6mm	8mm	7mm	9mm
92pp	6mm	7mm	6mm	8mm	7mm	10mm
96pp	6mm	7mm	7mm	9mm	8mm	10mm
100pp	6mm	8mm	7mm	9mm	8mm	10mm
104pp	6mm	8mm	7mm	9mm	8mm	11mm
108pp	6mm	8mm	7mm	10mm	8mm	11mm
112pp	7mm	8mm	8mm	10mm	9mm	12mm
116pp	7mm	9mm	8mm	10mm	9mm	12mm
120pp	7mm	9mm	8mm	10mm	9mm	12mm
124pp	7mm	9mm	8mm	11mm	10mm	13mm
128pp	7mm	10mm	9mm	11mm	10mm	13mm
132pp	7mm	10mm	9mm	11mm	10mm	14mm
136pp	8mm	10mm	9mm	12mm	10mm	14mm
140pp	8mm	10mm	9mm	12mm	11mm	14mm
144pp	8mm	11mm	10mm	12mm	11mm	15mm
148pp	8mm	11mm	10mm	13mm	11mm	15mm
152pp	8mm	11mm	10mm	13mm	12mm	15mm
156pp	9mm	12mm	10mm	13mm	12mm	16mm
160pp	9mm	12mm	11mm	14mm	12mm	16mm
164pp	9mm	12mm	11mm	14mm	13mm	17mm
168pp	9mm	12mm	11mm	14mm	13mm	17mm
172pp	9mm	13mm	11mm	15mm	13mm	17mm
176pp	10mm	13mm	12mm	15mm	13mm	18mm
180pp	10mm	13mm	12mm	15mm	14mm	18mm
184pp	10mm	14mm	12mm	16mm	14mm	19mm
188pp	10mm	14mm	12mm	16mm	14mm	19mm
192pp	10mm	14mm	13mm	16mm	15mm	19mm
196pp	11mm	14mm	13mm	17mm	15mm	20mm
200pp	11mm	15mm	13mm	17mm	15mm	20mm
204pp	11mm	15mm	13mm	17mm	15mm	20mm
208pp	11mm	15mm	14mm	18mm	16mm	21mm
212pp	11mm	15mm	14mm	18mm	16mm	21mm
216pp	12mm	16mm	14mm	18mm	16mm	22mm
220pp	12mm	16mm	14mm	18mm	17mm	22mm
224pp	12mm	16mm	15mm	19mm	17mm	22mm
228pp	12mm	17mm	15mm	19mm	17mm	23mm
232pp	12mm	17mm	15mm	19mm	18mm	23mm
236pp	13mm	17mm	15mm	20mm	18mm	24mm
240pp	13mm	17mm	16mm	20mm	18mm	24mm
244pp	13mm	18mm	16mm	20mm	18mm	24mm
248pp	13mm	18mm	16mm	21mm	19mm	25mm
252pp	13mm	18mm	16mm	21mm	19mm	25mm
256pp	14mm	19mm	17mm	21mm	19mm	26mm
260pp	14mm	19mm	17mm	22mm	20mm	26mm
264pp	14mm	19mm	17mm	22mm	20mm	26mm
268pp	14mm	19mm	17mm	22mm	20mm	27mm
272pp	14mm	20mm	18mm	23mm	20mm	27mm
276pp	15mm	20mm	18mm	23mm	21mm	27mm
280pp	15mm	20mm	18mm	23mm	21mm	28mm
284pp	15mm	21mm	18mm	24mm	21mm	28mm
288pp	15mm	21mm	19mm	24mm	22mm	29mm
292pp	15mm	21mm	19mm	24mm	22mm	29mm
296pp	16mm	21mm	19mm	25mm	22mm	29mm
300pp	16mm	22mm	19mm	25mm	23mm	30mm
304pp	16mm	22mm	20mm	25mm	23mm	30mm
308pp	16mm	22mm	20mm	26mm	23mm	31mm
312pp	16mm	23mm	20mm	26mm	23mm	31mm
316pp	17mm	23mm	20mm	26mm	24mm	31mm
320pp	17mm	23mm	21mm	27mm	24mm	32mm
324pp	17mm	23mm	21mm	27mm	24mm	32mm
328pp	17mm	24mm	21mm	27mm	25mm	32mm
332pp	17mm	24mm	21mm	27mm	25mm	33mm
336pp	17mm	24mm	22mm	28mm	25mm	33mm
340pp	18mm	25mm	22mm	28mm	25mm	34mm
344pp	18mm	25mm	22mm	28mm	26mm	34mm
348pp	18mm	25mm	22mm	29mm	26mm	34mm
352pp	18mm	25mm	23mm	29mm	26mm	35mm
356pp	18mm	26mm	23mm	29mm	27mm	35mm
360pp	19mm	26mm	23mm	30mm	27mm	36mm
364pp	19mm	26mm	24mm	30mm	27mm	36mm
368pp	19mm	26mm	24mm	30mm	27mm	36mm
372pp	19mm	27mm	24mm	31mm	28mm	37mm
376pp	19mm	27mm	24mm	31mm	28mm	37mm
380pp	20mm	27mm	25mm	31mm	28mm	37mm
384pp	20mm	28mm	25mm	32mm	29mm	38mm
388pp	20mm	28mm	25mm	32mm	29mm	38mm
392pp	20mm	28mm	25mm	32mm	29mm	39mm
396pp	20mm	28mm	26mm	33mm	30mm	39mm
400pp	21mm	29mm	26mm	33mm	30mm	39mm

Longer books, odd page counts, or an exact figure

Beyond 400 pages, or for a page count that isn't in the chart, the spine follows a simple line: a fixed thickness per page plus a small constant. Round to the nearest whole millimetre.

Spine (mm) = pages × k + c

Example: 64 inside pages on 120gsm Uncoated → 64 × 0.0705 + 0.54 = 5.05 → 5mm.

Inside paper	k (mm per page)	c (constant)	≈ per leaf
130gsm Silk / Gloss	0.0490	1.03	0.098mm
120gsm Uncoated	0.0705	0.54	0.141mm
150gsm Silk / Gloss	0.0627	0.68	0.125mm
140 / 150gsm Uncoated	0.0801	0.87	0.160mm
170gsm Silk / Gloss	0.0733	0.52	0.147mm
170gsm Uncoated	0.0967	0.75	0.193mm

Now build the files

Turning your spine size into a cover spread and inside pages

A perfect bound book needs two PDFs. The cover is one landscape spread with the spine running down the middle; the inside pages are single pages, one after another, in reading order. Here's the maths — with H for height, W for width and S for spine, all in millimetres.

Back cover + spine + front cover, left to right, on one page. Add 3mm bleed to every outside edge (never around the spine).

PDF 1

The cover spread

H × (W + S + W) mm, or (H + 6) × (W + S + W + 6) mm with the 3mm bleed on each edge. Back cover on the left, spine in the centre, front cover on the right. Supply a 1-page PDF, or 2 pages if your inside front and back covers are printed too.

PDF 2

The inside pages

H × W mm as single pages (not spreads), or (H + 6) × (W + 6) mm with bleed. The PDF should contain every inside page in reading order and nothing else — 40 inside pages means a 40-page PDF. Leave the covers out.

Worked examples

Two real books, start to finish

Example 1 · A5 zine

A5 · 40 inside pages · 130gsm Silk

Spine (40pp row, 130gsm Silk / Gloss)3mm
Cover spread: 148 + 3 + 148 = 299mm wide210 × 299mm
Cover spread with 3mm bleed216 × 305mm
Inside pages (with bleed)210 × 148mm (216 × 154mm)
Inside pages PDF40 pages

Example 2 · US Letter novel

279 × 216mm · 140 inside pages · 170gsm Uncoated

Spine (140pp row, 170gsm Uncoated)14mm
Cover spread: 216 + 14 + 216 = 446mm wide279 × 446mm
Cover spread with 3mm bleed285 × 452mm
Inside pages (with bleed)279 × 216mm (285 × 222mm)
Inside pages PDF140 pages

Standard trimmed sizes

Height first, as we quote them. Custom sizes work exactly the same way — take your trimmed height and width and add 6mm to each for the bleed size.

Size	Trimmed page (H × W)	Inside page artwork with 3mm bleed
A6	148 × 105mm	154 × 111mm
A5	210 × 148mm	216 × 154mm
A4	297 × 210mm	303 × 216mm
Square	210 × 210mm	216 × 216mm
Square	250 × 250mm	256 × 256mm
Square	294 × 294mm	300 × 300mm
US Letter	279 × 216mm	285 × 222mm

Spine design tips

Make the spine work hard on the shelf

The spine is the first thing most people see once your book is shelved. A few habits keep it looking sharp whatever the binder does on the day.

📏

Keep spine text small and centred

Binding has a natural tolerance of a millimetre or so. Text that sits comfortably inside the spine, with clear space either side, stays on the spine even if the book folds a fraction off centre.

⚠️

Under 5mm? Leave the text off

On a spine narrower than 5mm there simply isn't room for lettering to sit safely, and it risks sliding round onto the front or back cover. Let colour or a pattern do the talking instead.

🧷

Mind the glue on your first and last pages

The binding glue grips around 8mm of the first and last inside pages, so keep anything important — text, logos, faces — clear of that strip on those two pages.

🖼️

Images that cross the spine

A photo running from the back cover to the front looks brilliant — just remember 3–5mm disappears into the curve of the spine, so don't put a face or a headline right on the fold.

Good to know

Before you set up the file

📎

Stapled booklets have no spine

If your booklet is wire stitched (stapled), the whole thing is one PDF of single pages at the trimmed size plus 3mm bleed all round. No spread, no spine, nothing to calculate.

📚

Hardback books use different maths

A case bound cover wraps around thick boards, adds turn-ins and needs its own endpaper spreads, so the chart above doesn't apply. Tell us your spec and we'll send you the exact cover dimensions for your hardback.

🎯

A guide for artwork, confirmed at proof

Paper varies slightly from batch to batch, so a millimetre either way is normal. We confirm the final spine when we check your files, and if it needs a nudge we'll tell you before anything prints.

📄

Cover weight doesn't change it

The spine is dictated solely by the quantity and weight of your inside pages. Swap a 300gsm cover for 350gsm and the spine stays exactly the same — so choose your cover for feel and finish, not spine maths.

Quick answers

Spine size FAQs

What is the minimum page count for a perfect bound book?

We print perfect bound books from 32 pages in total — a 4-page cover plus 28 inside pages. Below that the spine is too thin to glue reliably, which is why the chart starts at 28 inside pages. Fewer pages than that? A stapled booklet is the answer.

My page count isn't in the chart. What do I do?

Take the nearest row — if you have 62 pages, the 60pp and 64pp rows tell you everything you need. For an exact figure, pop your numbers into the calculator or use the formula: pages × k + c, rounded to the nearest millimetre.

Do silk and gloss papers have different spine sizes?

Not in practice. Silk and gloss of the same weight are the same base sheet with a different surface, so they share a column in the chart. Uncoated papers are bulkier, which is why 120gsm uncoated makes a thicker spine than 130gsm silk.

Does the cover paper change the spine width?

No. The spine is set purely by the number of inside pages and the paper they're printed on — the cover simply wraps around that block, whatever its weight. Pick your cover stock for feel, finish and durability; the spine figure stays the same.

Do I add bleed to the spine?

No. The 3mm bleed goes on the outside edges of the cover spread only — top, bottom, left and right. The spine sits inside the spread, so it never gets bleed of its own.

Will you check my spine before printing?

Always. Every job gets a free file check, and the spine width is one of the first things we look at. If your page count or paper changes after you've set up the cover, just tell us and we'll give you the new figure.

Keep going

Next steps for your perfect bound book

Still not sure? Send us the file.

We check every file for free — spine, bleed, page order, the lot — and tell you exactly what to change before anything goes near a press. No obligation, no judgement.

Send your file for a free check Get a quote