what is a3 paper size
A3 is a standard ISO 216 paper size measuring 297 × 420 mm, which is about 29.7 × 42 cm or 11.7 × 16.5 inches.
What is A3 paper size?
A3 belongs to the ISO “A series” of paper sizes (A0, A1, A2, A3, A4, etc.) used worldwide for printing and office work. It is exactly half the size of A2 and twice the size of A4 when you cut or fold sheets along the longest side.
Key dimensions:
- 297 × 420 mm.
- 29.7 × 42 cm.
- Approximately 11.7 × 16.5 inches (often rounded from 11.69 × 16.54 in).
- Area: about 0.125 m² (or 1250 cm²).
How big is A3 in everyday terms?
Think of A3 as two A4 sheets side by side along their long edges. If you place two standard printer pages (A4) next to each other horizontally, that combined rectangle is roughly A3 size.
Some practical notes:
- Noticeably larger than a typical home/office document page (A4), but still easy to handle and pin on a wall.
- Fits into a C3 envelope flat; when folded in half (to A4), it fits into a C4 envelope.
Common uses of A3 paper
A3’s size makes it popular wherever more visual space is needed without going to very large poster formats:
- Small posters and wall notices.
- Restaurant menus and café boards.
- Brochures or folded leaflets that need big images or diagrams.
- Architectural or engineering sketches and layouts.
- School and college projects, charts, and artwork.
- Presentation visuals printed for meetings.
In design and print shops, A3 is often the “go-to” size when A4 feels cramped but A2 would be too large or expensive.
Quick reference table (A3 basics)
| Property | A3 value |
|---|---|
| Dimensions (mm) | 297 × 420 mm | [3][7][9][5]
| Dimensions (cm) | 29.7 × 42 cm | [9][3]
| Dimensions (inches) | ≈ 11.7 × 16.5 in (11.69 × 16.54 in) | [7][1][3][9][5]
| Area | ≈ 0.125 m² (1250 cm²) | [1][3]
| Relation to A4 | 2 × A4 sheets side by side | [9][5]
| Standard | ISO 216 A-series paper | [7][1][5]
Extra: pixels for A3 (useful for design)
When setting up a digital canvas for printing A3, designers often use these common resolutions:
- At 72 DPI: 842 × 1191 pixels.
- At 300 DPI (print quality): 3508 × 4960 pixels.
These values help you create sharp A3 posters, menus, or artwork without them looking blurred in print.
TL;DR: A3 paper is 297 × 420 mm (about 11.7 × 16.5 in), part of the ISO A-series, and is commonly used for small posters, menus, large brochures, and design layouts.
Information gathered from public forums or data available on the internet and portrayed here.
