Paper Size Reference
ISO A-series and common US paper sizes, in millimeters and inches.
Last updated
ISO A-series
| Size | Millimeters | Inches |
|---|
US sizes
| Size | Millimeters | Inches |
|---|
About this tool
The ISO 216 A-series is built on one rule: each size is exactly half of the one before it, cut along the long edge, and every size shares the same aspect ratio (1:√2 ≈ 1:1.414) — which is why an A4 sheet folded in half becomes an A5 sheet with identical proportions. US paper sizes (Letter, Legal, Tabloid) don't follow this rule and use a different, non-constant aspect ratio, which is why scaling a US Letter document to A4 (or vice versa) always crops or adds a small margin rather than matching exactly.
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