A4 vs US Letter
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
All of Europe, all of Asia, most of the world. ISO 216 standard.
US, Canada, parts of Mexico, the Philippines (parallel to A4). Chile, Colombia (mixed).
| Aspect | A4 | US Letter |
|---|---|---|
| Dimensions | 210 × 297 mm | 216 × 279 mm |
| In inches | 8.27 × 11.69 in | 8.5 × 11 in |
| Aspect ratio | √2 (1.414) | 1.294 |
| Bigger area | 6.25% bigger | — |
| Folder/binder size | A4 standard | Letter standard |
Frequently asked
Will an A4 document print on US Letter?
Yes, but with margin adjustments or scaling. If you print 'fit to page', expect some scaling. If you print at 100%, the bottom of an A4 document gets cut off on Letter, or the right of a Letter document gets cut off on A4.
Why does A4 have that weird ratio?
A4 is part of the ISO 216 A-series, where each size's aspect ratio is √2 ≈ 1.414. This means folding A4 in half gives you exactly A5 with the same aspect ratio. The system was designed in Germany in 1922 specifically for this scaling property.
Frequently asked questions
Will an A4 document print on US Letter?
Yes, but with margin adjustments or scaling. If you print 'fit to page', expect some scaling. If you print at 100%, the bottom of an A4 document gets cut off on Letter, or the right of a Letter document gets cut off on A4.
Why does A4 have that weird ratio?
A4 is part of the ISO 216 A-series, where each size's aspect ratio is √2 ≈ 1.414. This means folding A4 in half gives you exactly A5 with the same aspect ratio. The system was designed in Germany in 1922 specifically for this scaling property.