Yeah, this part trips people up more than it should.
You open Word or InDesign, see 20+ page sizes, Google says something different, your printer says something else… and suddenly your margins are off, your spine is wrong, and your book looks like it was printed at a photocopy shop in 2003.
I’ve fixed this mess more times than I can count.
Here’s the truth: page size is not just a design choice — it controls printing cost, trim accuracy, margins, and even whether your file gets rejected.
Let’s get you out of that confusion fast.
The #1 Mistake Authors Make (And Why It Ruins Everything)
They design in A4 or Letter… then try to “shrink it later.”
That never works cleanly.
Why?
Because when you resize:
- Margins shift
- Font sizes scale weirdly
- Line breaks change
- Page count changes (huge problem for print pricing)
Fix this now: pick your final trim size BEFORE you format anything.
Not after. Not “we’ll adjust later.” Now.
The Page Sizes That Actually Matter (Ignore the Rest)
Forget the giant list of paper sizes. For books, you’ll use maybe 5–6 sizes in real life.
Here’s the core set:
| Size Name | Inches | Best For |
|---|---|---|
| 5″ x 8″ | 5 × 8 | Short novels, memoirs |
| 5.5″ x 8.5″ | 5.5 × 8.5 | Standard fiction |
| 6″ x 9″ | 6 × 9 | Most popular — fiction + nonfiction |
| 7″ x 10″ | 7 × 10 | Workbooks, larger text |
| 8.5″ x 11″ | 8.5 × 11 | Manuals, textbooks |
| A5 | 5.83 × 8.27 | Europe / international printing |
If you’re stuck and just want a safe choice:
👉 Go with 6″ x 9″.
That’s the industry default for a reason.
Why 6″ x 9″ Keeps Showing Up Everywhere
This isn’t random.
Printers love it because:
- Efficient paper cutting (less waste)
- Standard trim workflows
- Predictable spine calculations
Readers like it because:
- Comfortable to hold
- Good balance of text density and readability
And platforms like KDP/Ingram?
They’re optimized for it.
Translation: fewer problems, fewer surprises.
A4 vs Letter vs Trim Size (The Confusion That Wastes Days)
This is where most people get stuck.
Let me simplify it:
- A4 (8.27 × 11.69) → Office documents
- Letter (8.5 × 11) → US office documents
- Trim Size (like 6 × 9) → Actual book size
Think of it like this:
A4/Letter = printer paper
Trim size = finished book
Designing a novel in A4 is like designing a passport photo on a billboard.
Wrong tool.
The Hidden Layer: Margins, Bleed, and Gutter (Where Books Actually Fail)
Page size alone isn’t enough. This is where beginners mess up hard.
Gutter (Inside Margin)
That space near the spine.
If it’s too small:
- Text disappears into the binding
- Readers have to force the book open
Rule of thumb:
- Under 150 pages → ~0.5″ gutter
- 150–300 pages → ~0.6–0.75″
- Thick books → even more
This depends on page count. Always.
Bleed (Only If You Have Images)
Bleed = extra area that gets trimmed off.
If your design touches the edge:
- You must add bleed (usually 0.125″)
If not:
- You’ll get white edges after trimming
No bleed needed for plain text books. Keep it simple.
Outer Margins
Don’t get fancy.
- Top: ~0.75″
- Bottom: ~0.75–1″
- Outside: ~0.5–0.75″
Consistency beats creativity here.
Choosing the Right Size Based on Book Type
Don’t overthink it. Match the size to how the book is used.
Fiction / Novels
- 5″ x 8″
- 5.5″ x 8.5″
- 6″ x 9″ (safe choice)
Nonfiction
- 6″ x 9″ (default)
- 7″ x 10″ (if diagrams/heavy content)
Workbooks / Journals
- 7″ x 10″
- 8.5″ x 11″
Children’s Books
- 8″ x 8″
- 8.5″ x 8.5″
- Custom sizes (but now printing gets trickier)
Academic / Manuals
- 8.5″ x 11″
The “Why Is My Book Rejected?” Section
Seen this hundreds of times.
Your file gets rejected because:
- Trim size in PDF doesn’t match platform settings
- No bleed where required
- Margins too small
- Wrong page dimensions (A4 uploaded as 6×9)
- Spine width doesn’t match page count
Most common one?
👉 Mismatch between document size and selected trim size.
Always double-check:
- Document setup
- Export settings
- Platform selection
All three must match exactly.
Fix It in 60 Seconds: Check Your Page Size Properly
Open your file and verify:
In Microsoft Word:
- Go to Layout → Size
- Click More Paper Sizes
- Check width + height manually
In InDesign:
- File → Document Setup
- Look at:
- Width
- Height
- Bleed settings
Do not trust templates blindly. Always check numbers.
When You Might Break the Rules (And Get Away With It)
Sometimes you want a unique size.
Fine. But understand the trade-offs:
- Higher printing cost
- Limited distribution options
- Possible trim inconsistencies
- Harder cover design
Custom sizes are not “wrong.”
They’re just less forgiving.
The One Thing I Wish Everyone Knew From Day One
Here it is:
Your page size decision locks everything else — margins, typography, page count, cover, printing cost.
Change it late, and you’re basically starting over.
Pick it early. Stick to it.
Still Unsure? Use This Shortcut
If you’re stuck between choices:
- Want simple, safe, widely accepted → 6″ x 9″
- Want compact novel feel → 5.5″ x 8.5″
- Need writing space or forms → 8.5″ x 11″
Don’t chase perfection.
Pick something proven and move forward.
You don’t need the “perfect” size. You need a compatible, printable, industry-safe size that won’t break later.
Get that right, and everything else becomes easier.