ISO 216 · A-series
A3 paper size — 297 × 420 mm
A3 is 297 × 420 millimetres — 29.7 × 42 cm, approximately 11.69 × 16.54 inches, and 3508 × 4961 pixels at 300 DPI. Exactly twice the area of A4, A3 is the go-to size for small posters, technical drawings and double-page spreads.
A3 — instant conversion
| Unit | Width | Height |
|---|---|---|
| Millimetres (mm) | 297 mm | 420 mm |
| Centimetres (cm) | 29.7 cm | 42 cm |
| Inches (in) | 11.693 in | 16.535 in |
| Pixels @ 300 DPI | 3508 px | 4961 px |
| PostScript points (pt) | 841.9 pt | 1190.6 pt |
| Picas | 70.16 | 99.21 |
Change the DPI selector to see the pixel resolution at 72, 96, 150, 200, 300 or 600 DPI. Physical dimensions (mm, cm, in, pt, picas) do not change with DPI.
A3 pixel sizes at every DPI
Because A3 is often used for posters, image resolution matters more than for office sizes. An image that looked sharp at A4 becomes visibly soft when enlarged to A3 — source your artwork at A3 dimensions from the start.
| DPI | Width (px) | Height (px) | Megapixels |
|---|---|---|---|
| 72 | 842 | 1191 | 1 MP |
| 96 | 1123 | 1587 | 1.8 MP |
| 150 | 1754 | 2480 | 4.3 MP |
| 200 | 2339 | 3307 | 7.7 MP |
| 300 | 3508 | 4961 | 17.4 MP |
| 600 | 7016 | 9921 | 69.6 MP |
Other units: 11.693 × 16.535 in, 841.9 × 1190.6 pt.
A3 · 297 × 420 mm
A3 vs A4 vs Tabloid
| Size | Millimetres | Inches | Notes |
|---|---|---|---|
| A2 | 420 × 594 | 16.54 × 23.39 | 2 × A3 — medium poster |
| A3 | 297 × 420 | 11.69 × 16.54 | (this page) |
| A4 | 210 × 297 | 8.27 × 11.69 | ½ × A3 |
| US Tabloid | 279.4 × 431.8 | 11 × 17 | US equivalent — 18 mm narrower, 12 mm taller |
Where A3 is used
- Small posters, event signage and shop displays
- Architectural and engineering drawings
- Magazine and newspaper double-page spreads
- Wall calendars and pin-up planners
- Design mood boards and layout proofs
- Children's art pads and classroom charts
A3 poster design specs
- Bleed
- 3 mm → export 303 × 426 mm (5 mm for some large-format shops)
- Safe area
- 5 mm inset — keep text inside 287 × 410 mm
- Headline size
- 36 pt+ for reading at 1–2 m
- Image resolution
- 3508 × 4961 px @ 300 DPI · 1754 × 2480 px acceptable @ 150 DPI
- Export format
- PDF/X-1a — flattens transparency, embeds fonts
Frequently asked questions
What are the exact dimensions of A3?
A3 is exactly 297 × 420 millimetres by ISO 216 — that is 29.7 × 42.0 cm, or approximately 11.69 × 16.54 inches. It is exactly twice the area of A4.
What is A3 in pixels?
At 300 DPI (commercial print) A3 is 3508 × 4961 pixels — about 17.4 megapixels. At 150 DPI (large-format posters viewed from a distance) it is 1754 × 2480 px. At 96 DPI it is 1123 × 1587 px.
Is A3 double A4?
Yes. Two A4 sheets (210 × 297 mm each) placed side by side along their long edges form exactly one A3 sheet (297 × 420 mm). The 1 : √2 aspect ratio is preserved.
Can a home printer print A3?
Most home printers max out at A4. A3 printing needs a wide-format printer — common in offices, copy shops, architecture firms and design studios. Online print services accept A3 PDFs as a standard preset, usually the cheapest small-poster option.
What is the US equivalent of A3?
US Tabloid (11 × 17 in / 279.4 × 431.8 mm) fills the same role. Tabloid is about 18 mm narrower and 12 mm taller than A3 — close but not interchangeable. A design for one needs adjusting for the other.
What is A3 used for?
Small posters, architectural and engineering drawings, magazine double-page spreads, wall calendars, mood boards, restaurant menus, exam papers with extra working space, and children's drawing pads.
What is A3 in cm?
A3 is 29.7 × 42.0 centimetres. Handy anchor: the short edge of A3 (29.7 cm) equals the long edge of A4.
What resolution do I need for an A3 poster?
A full-bleed A3 image at 300 DPI is 3508 × 4961 pixels (~17.4 MP). For posters viewed from more than 1.5–2 m away, 150 DPI (1754 × 2480 px) looks identical to the eye and halves the file size.
What bleed does an A3 poster need?
3 mm on each side is standard, making the export 303 × 426 mm. Some large-format printers ask for 5 mm — check the printer's spec sheet before exporting.
What is A3+ (Super A3)?
A3+ (also called Super B) is an unofficial size around 329 × 483 mm (13 × 19 in), used by photo inkjet printers to print full-bleed A3 images with room for trimming. It is not part of ISO 216.