A4 vs US Letter: What's the Difference, and Which Do You Need?
August 2, 2026
If you've ever printed a document and found the margins looked slightly off, there's a good chance the file was formatted for the wrong paper size. A4 and US Letter are close enough in size that most people never notice the difference — until a print job doesn't quite fit.
The actual size difference
A4 is 210mm × 297mm (8.27in × 11.69in). US Letter is 8.5in × 11in (215.9mm × 279.4mm).
A4 is slightly narrower and noticeably taller than Letter. In practice, a document formatted for one size and printed on the other will either have its content cut off at the bottom or end up with unexpectedly wide margins — the classic sign of a size mismatch.
Which regions use which
- A4: the UK, Europe, Asia, Australia, and most of the world use A4 as the standard size for everyday printing.
- US Letter: the United States, Canada, and a handful of other countries in the Americas use Letter as their default.
If you're not sure which one your printer expects, check your printer's paper tray settings or your operating system's default print settings — most are already configured for whichever size is standard in your region.
Why it matters for personalized printables
A4 and US Letter aren't interchangeable when you're printing something with fixed layout — like ruled lines, a music staff, or a graph grid that needs to reach cleanly to the edges of the page. A page designed for A4 and printed on Letter paper (or vice versa) can end up with an extra strip of blank space at the bottom, or ruling that runs slightly off the printable area.
That's why Paiper lets you pick your paper size up front, labelled by region rather than by name alone — A4 (UK / Asia) or US Letter (USA) — so the note paper, manuscript paper, or graph paper you build is sized correctly for your printer from the start, with the ruling and margins generated to fit that exact page size.
Quick reference
| A4 | US Letter | |
|---|---|---|
| Size (mm) | 210 × 297 | 215.9 × 279.4 |
| Size (inches) | 8.27 × 11.69 | 8.5 × 11 |
| Common in | UK, Europe, Asia, Australia | USA, Canada |
Not sure which one you need? If you're printing at home or at the office and don't know offhand, check a piece of paper already in your printer tray, or look at your print dialog's default page size — it'll usually tell you.