How many pages must my file have to match the spine of the book?

The thickness of the spine of a book is directly dependent on the number of pages, the type of paper y its grammage.
To ensure that your cover is perfectly aligned and the spine is neither too wide nor too narrow, it is important to calculate it accurately before sending us your file.

In this guide we explain how to do it in a simple way using approximate formulas based on the papers we use in our printing shop.

🟪 Simplified formula for calculating the back

You can calculate the thickness of the back with this formula:

Spine (mm) ≈ number of pages × paper thickness per page + 0.5 mm (margin for hot-melt)

⚠️ Important note:
These values are approximate. Depending on the paper, humidity or compression during binding, the actual result may vary slightly.

🟪 Approximate thickness per paper type

We use different papers for interiors, and each has a different thickness. Here are the approximate recommended values:

🟩 White bond (75-90 g)

Thickness per page: 0.05 mm
Formula:
Spine = pages × 0.05 + 0.5

Example:
200 pages → 200 × 0.05 + 0.5 =. 10.5 mm

🟩 Bond cultural / boned 90 g

Thickness per page: 0.055 mm
Formula:
Spine = pages × 0.055 + 0.5

Example:
240 pages → 240 × 0.055 + 0.5 =. 13.7 mm
(It is recommended to round to 14 mm)

🟩 Couché matte 130 g

Thickness per page: 0.06 mm
Formula:
Spine = pages × 0.06 + 0.5

Example:
120 pages → 120 × 0.06 + 0.5 =. 7.7 mm

🟩 Couché glossy 150 g

Thickness per page: 0.07 mm
Formula:
Spine = pages × 0.07 + 0.5

Example:
160 pages → 160 × 0.07 + 0.5 =. 11.7 mm

🟪 What if the calculation does not match exactly?

Small variations are normal due to:

Paper compression with ream
Natural variation in the thickness of each batch
Hot-melt glue setting
Type of binding

That is why we always recommend:

Round up slightly
Send the cover file in editable PDF
Allow our team to adjust the back if necessary

🟪 Do I have to calculate the spine myself?

You have two options:

✔️ Option 1: Calculate it yourself using the above formulas

Ideal if you want to prepare a complete cover (front cover + spine + back cover) ready to print.

✔️ Option 2: Send us your cover without spine and we will calculate it.

You can send:

Separate cover
Separate back cover
Final interior PDF

Our team can calculate the exact spine based on the chosen paper and the final pages.

🟪 Practical examples by type of book

📘 Book of 300 pages in cultural bond 90 g:

300 × 0.055 + 0.5 = 17 mm spine

📕 Illustrated book of 140 pages in 130 g matt couché:

140 × 0.06 + 0.5 = 8.9 mm → round up to 9 mm

200-page technical manual on 75 g white bond:

200 × 0.05 + 0.5 = 10.5 mm

🟪 Useful links

🟦 Conclusion

The spine of the book depends on how many pages your file has and the type of paper you choose.
With our simplified formulas you will be able to calculate it easily, but always remember that these are approximations.
If you wish, we can also calculate the exact spine for you by reviewing your files.