A4 vs US Letter: What's the Difference?
A4 and US Letter are the two most common paper sizes in the world. A4 is used throughout most of the world (including the UK), while US Letter is used in the United States, Canada and Mexico. Though they look similar, their dimensions and proportions differ — and this matters for printing, design and international trade.
• A4: 210 × 297 mm (8.27 × 11.69 in)
• US Letter: 216 × 279 mm (8.5 × 11 in)
• A4 is narrower and taller
• A4 has slightly more total area
📏 Side-by-Side Comparison
| Measurement | A4 | US Letter |
|---|---|---|
| Millimetres | 210 × 297 mm | 216 × 279 mm |
| Centimetres | 21.0 × 29.7 cm | 21.6 × 27.9 cm |
| Inches | 8.27 × 11.69 in | 8.5 × 11 in |
| Aspect Ratio | 1:1.414 (√2) | 1:1.294 |
| Area | 62,370 mm² | 60,264 mm² |
🎨 Key Differences
1. Aspect Ratio
A4 uses the ISO 216 √2 aspect ratio (1:1.414), which means folding any A-size in half gives you the next size down exactly. US Letter does not follow any consistent ratio — it's simply 8.5 × 11 inches.
2. Width and Height
A4 is about 6 mm narrower and 18 mm taller than US Letter. That means content designed for one size may not fit exactly on the other without scaling or content being cut off.
3. Global Usage
A4 is the standard in most of the world, while US Letter is used only in the US, Canada and Mexico. If you're doing business internationally, A4 is the safer default.
🖨️ Printing A4 on US Letter (or Vice Versa)
If you're printing A4 content on US Letter paper (or the reverse), you have a few options:
- Scale to fit: The printer will scale content down to about 94% to fit. Simple, but can create white borders.
- Print without scaling: Content may be clipped at the edges — usually not recommended.
- Use "shrink oversized pages": Adobe Acrobat and most PDF readers offer this option.
- Change the source document: Reformat the document to the target size before printing.
📊 Which Paper Size Should You Use?
| Scenario | Recommended Size |
|---|---|
| UK / EU business documents | A4 |
| US business documents | US Letter |
| International printing | A4 ⭐ |
| Designing for global audience | A4 (most compatible) |
| Canadian documents | US Letter (standard) |
💡 Common Misconceptions
- "A4 and Letter are the same" — They're not. A4 is 6 mm narrower and 18 mm taller.
- "A4 is bigger than Letter" — Actually, A4 has slightly more area, but Letter is wider.
- "You can freely swap them" — Documents often need to be reformatted, not just scaled.
📚 Frequently Asked Questions
Is A4 the same as US Letter?
No. A4 is 210 × 297 mm while US Letter is 216 × 279 mm. A4 is slightly narrower and taller.
Which is bigger, A4 or Letter?
A4 has slightly more total area. A4 is narrower but taller than Letter.
Can I print A4 on US Letter paper?
Yes, but the printer will typically scale the content down to about 94% to fit on Letter paper.
Why does the US use Letter instead of A4?
The US, Canada, and Mexico use their own paper standards based on traditional imperial measurements.