Letter vs A4: Size Difference Explained
US Letter is 8.5 × 11 inches (216 × 279 mm). A4 is 8.27 × 11.69 inches (210 × 297 mm). Letter is 6mm wider; A4 is 18mm taller. Here’s the complete comparison.
Side-by-Side Comparison
| Property | US Letter | A4 | Difference |
|---|---|---|---|
| Width (inches) | 8.5 | 8.27 | Letter is 0.23” wider |
| Height (inches) | 11 | 11.69 | A4 is 0.69” taller |
| Width (mm) | 216 | 210 | Letter is 6mm wider |
| Height (mm) | 279 | 297 | A4 is 18mm taller |
| Area (sq inches) | 93.5 | 96.67 | A4 has 3.4% more area |
| Area (sq mm) | 60,264 | 62,370 | A4 has 3.5% more area |
| Aspect Ratio | 1:1.294 | 1:1.414 (1:√2) | A4 is proportionally taller |
| Pixels @ 300 DPI | 2550 × 3300 | 2480 × 3508 | — |
Visual Difference
If you overlay the two sizes, A4 extends 18mm (about 0.7 inches) beyond Letter at the bottom, while Letter extends 6mm (about 0.25 inches) beyond A4 on the right side.
Where Each Size Is Used
US Letter is the standard in:
- United States
- Canada
- Parts of Mexico and the Philippines
A4 is the standard in:
- Europe (all countries)
- United Kingdom
- Australia and New Zealand
- Asia (Japan, China, India, South Korea)
- South America (most countries)
- Africa (most countries)
Printing Across Sizes
When printing a document designed for one size on the other:
| Scenario | Result | Solution |
|---|---|---|
| A4 doc → Letter paper | Bottom may be cut off | Use “Fit to Page” or “Shrink to Fit” |
| Letter doc → A4 paper | Extra space at bottom | Use “Fit to Page” or adjust margins |
| PDF designed for A4 | May not fill Letter width | Usually acceptable — margins differ slightly |
Why the Difference Exists
The A4 standard comes from ISO 216 (adopted 1975), based on a German DIN standard from 1922. The system uses a mathematical ratio of 1:√2, meaning each A-size is exactly half the next larger size.
US Letter size has no such mathematical basis — its dimensions evolved from traditional American papermaking practices. Despite international standardization efforts, the US has never adopted ISO 216.
Which Should You Use?
- For US audiences: Use Letter
- For international audiences: Use A4
- For web/PDF distribution globally: Design for A4 (it’s taller, so Letter users get more margin at the bottom, which is less disruptive than cutting off content)
For more on US sizes, see US Paper Sizes. For the full A series, see A Series Paper Sizes.
Frequently Asked Questions
What is the difference between Letter and A4 paper?
US Letter (8.5 x 11 inches / 216 x 279mm) is 6mm wider and 18mm shorter than A4 (8.27 x 11.69 inches / 210 x 297mm). A4 has about 3.4% more area than Letter.
Can I print an A4 document on Letter paper?
Yes, but the content may be slightly cut off or scaled down. Most printers offer a 'Fit to Page' option that scales the document to fit the paper size. The top and bottom margins will be tighter since Letter is shorter than A4.
Which countries use Letter vs A4?
The US, Canada, and parts of Mexico and the Philippines use Letter size. Nearly all other countries worldwide use A4 as their standard paper size, following the ISO 216 standard.