⚖️ Comparison · Updated for 2026
A4 vs US Letter
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
Quick answer: A4 is 210 × 297 mm (8.27 × 11.69 in). US Letter is 8.5 × 11 in (216 × 279 mm). A4 is slightly narrower and noticeably taller. Documents print differently on each — fitting US Letter content onto A4 may need scaling or page-break adjustments.
Decision guide — when to use which
Use A4 when…
All of Europe, all of Asia, most of the world. ISO 216 standard.
Use US Letter when…
US, Canada, parts of Mexico, the Philippines (parallel to A4). Chile, Colombia (mixed).
📊 Side-by-side comparison
| 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
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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.
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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.
Reviewed for 2026. All conversion factors and historical references verified against official sources (ISO standards, government weights & measures legislation, IEC technical specifications). Built by a UK-based qualified primary teacher and FA Level 2 coach as part of 247QuickTools' free utility-tools project. We don't sell SEO links or accept paid placements in this content.