ISO 216 · A-series
A4 paper size
A4 is the world's most-used paper size. It measures exactly 210 × 297 millimetres and is the default for office printers, schools and home documents almost everywhere outside North America. Its aspect ratio of 1 : √2 means folding an A4 sheet in half produces a perfectly proportioned A5.
Exact dimensions
All units are listed below. Pixel values assume the page is rendered at the listed DPI. For commercial printing, 300 DPI is the usual target; for web and on-screen viewing, 72 or 96 DPI is standard.
| Unit | Width | Height |
|---|---|---|
| Millimetres (mm) | 210 | 297 |
| Centimetres (cm) | 21 | 29.7 |
| Inches (in) | 8.268 | 11.693 |
| Pixels @ 72 DPI | 595 | 842 |
| Pixels @ 96 DPI | 794 | 1,123 |
| Pixels @ 150 DPI | 1,240 | 1,754 |
| Pixels @ 200 DPI | 1,654 | 2,339 |
| Pixels @ 300 DPI | 2,480 | 3,508 |
| Pixels @ 600 DPI | 4,961 | 7,016 |
A4 — 210 × 297 mm
Where A4 is used
A4 is the default office and school paper size across the European Union, the United Kingdom, most of Asia, Africa, Australia and South America. Government forms, contracts, CVs, university essays and printer-friendly PDFs are nearly always sized to A4.
If you are publishing a document for an international audience, A4 is the safer default. Most US printers can still load A4, but the reverse is not always true.
A4 vs US Letter
US Letter (216 × 279 mm) is slightly wider and noticeably shorter than A4. The difference is small enough that text-heavy documents usually reflow cleanly, but layouts with edge-aligned graphics, headers or page numbers will shift. If a document needs to look identical on both sizes, design margins generously and avoid placing critical content within 15 mm of any edge.
Designing for A4 print
Bleed and margins
For full-bleed prints (artwork that reaches the edge), extend the design 3 mm past the trim on every side, so the final document is 216 × 303 mm. Keep important text at least 5 mm inside the trim line.
Pixel resolution for print
At 300 DPI, an A4 page is 2480 × 3508 pixels. That is the minimum size for any raster image you want to span the full page without visible pixellation.
Common margin values
Office documents typically use 25 mm (1 inch) margins. Tight layouts can drop to 15 mm. Wider 30–35 mm margins are common for academic theses and long-form reading.
Folding to A5 or A6
A4 folded in half along the long edge gives A5 (148 × 210 mm). Folded again gives A6 (105 × 148 mm). Every fold preserves the same 1 : √2 proportions.
Frequently asked questions
What are the exact dimensions of A4?
A4 is 210 × 297 millimetres, which is 21.0 × 29.7 centimetres, or approximately 8.27 × 11.69 inches. The aspect ratio is 1 : √2 (about 1 : 1.414).
How many pixels is an A4 page?
It depends on the DPI (dots per inch). At 300 DPI, which is standard for print, an A4 page is 2480 × 3508 pixels. At 72 DPI (web), it is 595 × 842 pixels. The full table is in the dimensions section above.
Why does A4 have such an unusual aspect ratio?
The 1 : √2 ratio is intentional: when you fold an A4 sheet in half along its long edge you get exactly an A5 sheet with the same proportions. The same is true for every A-series step. This makes scaling between sizes lossless and is the reason the ISO A-series exists.
Is A4 used in the United States?
Rarely. The US, Canada and parts of Mexico use US Letter (216 × 279 mm) instead. A4 is the standard almost everywhere else in the world.
Can I print A4 on a US Letter printer?
Most modern printers handle both, but you may need to switch the paper-tray setting and reload paper. Documents designed for A4 will have slightly different margins when printed on Letter, since A4 is taller and narrower.