| Unit | Width | Height |
|---|---|---|
| Millimeters (mm) | 215.9 | 279.4 |
| Centimeters (cm) | 21.59 | 27.94 |
| Inches (in) | 8.5 | 11 |
| Pixels @72dpi | 612 | 792 |
| Pixels @150dpi | 1275 | 1650 |
| Pixels @300dpi | 2550 | 3300 |
| Feet | 0.708 | 0.917 |
| A4 | Letter | |
|---|---|---|
| Size | 210×297mm | 215.9×279.4mm |
| Inches | 8.27×11.69" | 8.5×11" |
| Ratio | 1:√2 (1.414) | 1:1.294 |
| Used in | Most countries | US, Canada |
Letter is 6mm wider but 18mm shorter than A4. A4 has a 1:√2 ratio while Letter has 1:1.294 means it stays proportional when folded or scaled — a key advantage of the ISO 216 standard.
When printing a Letter document on A4, the bottom may be slightly cut off. When printing A4 on Letter, small side margins may appear.