Perfect Bind Book - Meaning of Open Size & Close Size

Using the infographic above, Open Size and Close Size refer to two different stages of the book:

📖 Close Size (Finished Book Size)

The Close Size is the final size of the book after it has been bound and closed.

In this example:

• Width: 210 mm

• Height: 210 mm

This means when someone is holding the finished book, the physical dimensions are:

210 mm × 210 mm

Think of it as:

"What size will my finished book be in my customer's hands?"

📖 Open Size (Flat Cover Layout)

The Open Size refers to the entire cover artwork laid flat before binding.

It includes:

• Back Cover

• Spine

• Front Cover

In this example:

Section	Width
Back Cover	210 mm
Spine	10 mm
Front Cover	210 mm
Total Width	430 mm

Height remains:

210 mm

Therefore the Open Size is:

430 mm × 210 mm

Think of it as:

"What size artwork should the designer create for printing?"

How the Calculation Works

For a perfect bound book:

Open Width = Back Cover + Spine + Front Cover

Using the infographic:

210+10+210=430

Therefore:

• Open Size = 430 mm × 210 mm

• Close Size = 210 mm × 210 mm

Why Designers Need Both Measurements

Designer Uses Open Size

The designer creates one continuous artwork measuring:

430 mm × 210 mm

This allows images, colors, and graphics to flow seamlessly across:

• Back cover

• Spine

• Front cover

Printer Uses Close Size

The printer needs the finished book dimensions:

210 mm × 210 mm

to:

• Cut the pages correctly

• Bind the book accurately

• Package and ship the finished product

Important Note About Spine Width

The infographic shows a 10 mm spine only as an example.

In reality, the spine width depends on:

• Number of pages

• Paper thickness (GSM)

• Paper bulk

• Binding method

For example:

Pages	Approx. Spine
40 pages	3–4 mm
80 pages	6–8 mm
120 pages	10–12 mm
200 pages	16–20 mm

As the page count increases, the Open Size becomes wider, while the Close Size remains 210 mm × 210 mm.

Simple Rule

✅ Close Size = Finished book size after binding.

✅ Open Size = Full cover artwork size before binding (Back Cover + Spine + Front Cover).

For the book shown in the infographic:

• Close Size: 210 mm × 210 mm

• Open Size: 430 mm × 210 mm (including 10 mm spine)