A4 paper measures 210 × 297 mm — 21.0 × 29.7 cm, or 8.27 × 11.69 inches. It is the international standard sheet defined by ISO 216 and the default page size almost everywhere outside the United States and Canada, where US Letter takes its place.
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The same sheet expressed in every unit you are likely to need.
| Unit | Width | Height |
|---|---|---|
| Millimetres | 210 mm | 297 mm |
| Centimetres | 21.0 cm | 29.7 cm |
| Inches | 8.27 in | 11.69 in |
| Points (72 dpi) | 595 pt | 842 pt |
| Pixels at 72 PPI | 595 px | 842 px |
| Pixels at 150 PPI | 1240 px | 1754 px |
| Pixels at 300 PPI | 2480 px | 3508 px |
Quick answer: A4 is 210 × 297 mm (8.27 × 11.69 in). Its area is exactly 1/16 of a square metre, and its sides are in a 1:√2 ratio — which is why folding an A4 sheet in half gives you a perfect A5.
The two dominant office sheet sizes are close but not interchangeable, which is why documents shift when they cross the Atlantic.
| Size | Millimetres | Inches | Difference vs A4 |
|---|---|---|---|
| A4 | 210 × 297 mm | 8.27 × 11.69 in | — |
| US Letter | 216 × 279 mm | 8.5 × 11 in | 6 mm wider, 18 mm shorter |
| US Legal | 216 × 356 mm | 8.5 × 14 in | 6 mm wider, 59 mm longer |
Printing an A4 document on Letter paper crops roughly 18 mm from the foot of the page unless you enable "fit to page"; printing Letter on A4 leaves a 6 mm strip of white down one side. For anything with a fixed layout — contracts, forms, certificates — set the page size before you design, not at the printer.
Every A size is the previous one folded in half across its longer side. A0 starts at exactly one square metre.
| Size | Millimetres | Inches | Relation to A4 |
|---|---|---|---|
| A0 | 841 × 1189 mm | 33.1 × 46.8 in | 16 × A4 |
| A1 | 594 × 841 mm | 23.4 × 33.1 in | 8 × A4 |
| A2 | 420 × 594 mm | 16.5 × 23.4 in | 4 × A4 |
| A3 | 297 × 420 mm | 11.7 × 16.5 in | 2 × A4 |
| A4 | 210 × 297 mm | 8.27 × 11.69 in | — |
| A5 | 148 × 210 mm | 5.83 × 8.27 in | Half of A4 |
| A6 | 105 × 148 mm | 4.13 × 5.83 in | Quarter of A4 |
Because the aspect ratio stays at 1:√2 through the whole series, scaling artwork between sizes never changes the proportions. A4 to A3 is exactly 141%; A4 to A5 is exactly 71%. Those are the two magnification presets you will find on any photocopier sold outside North America. See the full paper sizes guide for the B and C series.
Practical capacities for the jobs A4 is most often used for.
| Use | Typical capacity |
|---|---|
| Body text at 11 pt, single spaced | Around 500 words with 25 mm margins |
| Body text at 12 pt, double spaced | Around 250 words |
| Standard printer margins | Printable area roughly 190 × 277 mm |
| Photos at 4 × 6 in | 2 per sheet |
| Business cards (85 × 55 mm) | 10 per sheet |
| Weight of one 80 gsm sheet | 5.0 g (a 500-sheet ream is 2.5 kg) |
The 80 gsm weight is the office default. Because A4 is exactly 1/16 m², gsm converts to sheet weight by simple division: 80 gsm ÷ 16 = 5 g per sheet. That relationship is the reason the ISO system uses grams per square metre at all.
A4 is 21.0 cm wide and 29.7 cm high. In millimetres that is 210 × 297 mm, and in inches 8.27 × 11.69 in.
8.27 × 11.69 inches. It is slightly narrower and noticeably taller than US Letter, which is 8.5 × 11 inches.
No. A4 is 210 × 297 mm and US Letter is 216 × 279 mm. A4 is about 6 mm narrower and 18 mm taller, so a document laid out for one will not print correctly on the other without scaling.
It depends on the resolution: 595 × 842 px at 72 PPI, 1240 × 1754 px at 150 PPI, and 2480 × 3508 px at 300 PPI. Use 300 PPI for anything going to a commercial printer.
Because A0 is defined as one square metre with sides in a 1:√2 ratio, and each subsequent size halves the previous one. Four halvings from A0 land on 210 × 297 mm, and the ratio is preserved at every step.
A5, at 148 × 210 mm (5.83 × 8.27 in). Fold an A4 sheet across its long side and you have an A5 page — the reason A5 is the standard notebook and booklet format.
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