What A4 is used for
- Office and home printer paper in Europe, Asia, Africa, Oceania and South America
- Letters, forms, reports, school worksheets
- Exercise books and notepads (with A5 as the folded half)
A4 vs US Letter
A4 is 5.9 mm (0.23 in) narrower and 17.6 mm (0.69 in) taller than Letter. A document laid out for one usually prints on the other with a scaling of about 94–97%, or with uneven margins at 100%.
Landscape A4
Turned sideways A4 is 297 × 210 mm. The dimensions do not change, only the orientation.
Where the size comes from
ISO 216 defines A0 as one square metre with sides in the ratio 1 : √2. Halving the long side gives the next size, and the ratio stays the same: A4 is A0 halved four times, 1/16 m².
Questions
How big is A4 in pixels?
2480 × 3508 px at 300 dpi (print quality), 1240 × 1754 px at 150 dpi and 595 × 842 px at 72 dpi.
Is A4 the same as 8.5 × 11?
No. 8.5 × 11 in is US Letter (215.9 × 279.4 mm). A4 is 8.27 × 11.69 in.
How many A4 sheets make an A3?
Two. A3 (297 × 420 mm) is two A4 sheets side by side along their long edge.