Letter vs A4 Paper Size Comparison
Side-by-side comparison of the two most common paper sizes in the world.
| Property | US Letter | ISO A4 |
|---|---|---|
| Width (mm) | 215.9 mm | 210 mm |
| Height (mm) | 279.4 mm | 297 mm |
| Width (inches) | 8.5 in | 8.27 in |
| Height (inches) | 11 in | 11.69 in |
| Aspect Ratio | 1:1.294 | 1:1.414 |
| Area | 603.2 cm2 | 623.7 cm2 |
| Standard | ANSI | ISO 216 |
| Used In | US, Canada, Mexico, Philippines | Rest of the world |
| Pixels (300 DPI) | 2550 x 3300 | 2480 x 3508 |
Key Differences
- Letter is wider (5.9 mm / 0.23 in wider)
- A4 is taller (17.6 mm / 0.69 in taller)
- A4 has slightly more area (623.7 vs 603.2 cm2)
- A4 has a mathematical aspect ratio (1:sqrt 2)
- Letter dimensions are based on imperial measurements
Design Tips
- For international documents, design for A4 with Letter-safe margins
- Keep important content within 200 x 270 mm to fit both
- Set PDF export to include both size options
- When printing abroad, always check the default paper size
Which Should You Use?
If your audience is primarily in the United States, Canada, or Mexico, use Letter size. For international audiences or formal/academic documents, A4 is the standard. Many multinational companies create documents that work on both sizes by using conservative margins.