US Letter vs A4: PDF Page Size Differences and How to Check Yours
Letter and A4 look almost the same until you print one on the other's paper: the margins shift, the footer gets cut, and a "fit to page" scaling quietly shrinks everything. Knowing the real difference makes it easy to avoid.
The two sizes side by side
| US Letter | A4 | |
|---|---|---|
| Millimetres | 215.9 x 279.4 | 210 x 297 |
| Inches | 8.5 x 11 | 8.27 x 11.69 |
| PDF points | 612 x 792 | 595.28 x 841.89 |
Letter is 5.9 mm wider and 17.6 mm shorter than A4. That is a short, wide page against a tall, narrow one.
What goes wrong when they are mixed
- A4 file on Letter paper: the bottom 17.6 mm does not fit, so the printer either crops it or scales the whole page to about 94%.
- Letter file on A4 paper: there is a blank strip along the bottom and the page is 5.9 mm too wide, so the right margin shrinks.
Check which one your PDF is
- Open the PDF in PdfRuler.
- Read the size at the bottom right. 215.90 x 279.40 mm is Letter, 210.00 x 297.00 mm is A4.
- Switch the unit to in to confirm: 8.50 x 11.00 is Letter.
Designing for both
If a document will be printed in both regions, keep important content inside a safe area that fits both: at least 20 mm from every edge works. Use ruler guides to drag a margin line onto the page and check nothing crosses it. More sizes are in the PDF page size reference.
Frequently asked questions
Is US Letter bigger than A4?
Letter is wider (215.9 mm against 210 mm) but shorter (279.4 mm against 297 mm), so A4 has a slightly larger area.
Can I print an A4 PDF on Letter paper?
Yes, but the page is 17.6 mm taller than Letter, so the printer shrinks it to about 94% or crops the bottom. Choose "fit" or "actual size" deliberately.
How do I see if a PDF is Letter or A4?
Open it in PdfRuler and read the page size shown at the bottom right. 8.50 x 11.00 in is Letter; 210 x 297 mm is A4.
