A4 vs Letter
A4 is 6 mm narrower and 18 mm taller than US Letter. They share a printer tray, not a layout: a document built for one loses an edge or gains a margin band on the other.
Compare a Different Pair
A4 and Letter, Side by Side
| A4 | Letter | Difference | |
|---|---|---|---|
| Millimetres | 210 × 297 | 215.9 × 279.4 | 5.9 × 17.6 mm |
| Inches | 8.27 × 11.69 | 8.5 × 11 | 0.23 × 0.69 in |
| Centimetres | 21.0 × 29.7 | 21.6 × 27.9 | |
| Area | 0.0624 m², 62,370 mm² | 0.0603 m², 60,322 mm² | 1.03× |
| Aspect ratio | 1 : 1.414 (√2) | 1 : 1.294 | different |
What Is Lost Printing One on the Other
At 100% scale, both centred, nothing resized. A positive figure on the wider or taller side is cropped; on the other it is a blank margin.
| Axis | Gap | A4 onto Letter | Letter onto A4 |
|---|---|---|---|
| Width | 3 mm (0.12 in) each side | blank band | Letter loses it |
| Height | 8.8 mm (0.35 in) each end | A4 loses it | blank band |
Scale-to-Fit Percentages
The figure to type into a printer or PDF dialog to scale one to fit inside the other:
| Letter to fit A4 | 97% | leaves a thin border on one pair of edges |
|---|---|---|
| A4 to fit Letter | 94% | leaves a thin border on one pair of edges |
Which Should You Use?
Outside the US and Canada, use A4. Inside them, use Letter. For a file that crosses the border, fix the size in the template and tell the other side, rather than letting each print dialog decide.
Beyond the Measurements
Envelopes: A4 fits C4, C5, DL; Letter fits #10, 9 × 12, 6 × 9.
An A4 letter folded in three drops into a DL envelope and posts at the standard letter rate. Folded once it fits C5; flat and unfolded it needs a C4, which Royal Mail rates as a large letter up to 100 g. In the US an A4 sheet in a 9 x 12 in envelope goes as a flat.
Worth Knowing
This is the most common paper-size problem there is, and it is almost always caught too late, at the printer, when a footer is already missing. The fix is dull and it works: set the page size in the shared template, not per person and not in the print dialog. If you genuinely have to serve both, keep the content inside the area the two share, roughly 200 mm wide by 279 mm tall, and one file prints cleanly on either. "Fit to page" is a patch, not a plan: it rescales the whole document by a few percent, so measured sizes stop being measured.
Frequently Asked Questions
Is A4 bigger than Letter?
A4 is bigger. It is 210 × 297 mm against 215.9 × 279.4 mm for Letter, about 1.03 times the area.
What is the difference between A4 and Letter?
A4 is 6 mm narrower and 18 mm taller than US Letter. They share a printer tray, not a layout: a document built for one loses an edge or gains a margin band on the other.
Can you print Letter on A4?
Not at full size without a change. Shrink Letter to 97% to fit A4, which leaves a thin border, or print at 100% and lose 3 mm off each side and 8.8 mm top and bottom.
✓ Dimensions per the standards on the A4 and Letter pages. Differences and scale factors computed. Reviewed . Editorial Process →