A series paper sizes: A0 to A10
The A series starts at A0, which measures 841 × 1189 mm and has an area of exactly one square metre. Each following size is half the previous one: A1 is 594 × 841 mm, A4 is 210 × 297 mm, and A10 is just 26 × 37 mm.
Contents of this page
All A sizes with dimensions
| Size | mm | cm | inches | Area | Pixels at 300 dpi |
|---|---|---|---|---|---|
| 4A0 | 1682 × 2378 mm | 168.2 × 237.8 cm | 66.22 × 93.62 in | 3.9998 m² | 19,866 × 28,087 px |
| 2A0 | 1189 × 1682 mm | 118.9 × 168.2 cm | 46.81 × 66.22 in | 1.9999 m² | 14,043 × 19,866 px |
| A0 | 841 × 1189 mm | 84.1 × 118.9 cm | 33.11 × 46.81 in | 0.9999 m² | 9933 × 14,043 px |
| A1 | 594 × 841 mm | 59.4 × 84.1 cm | 23.39 × 33.11 in | 0.4996 m² | 7016 × 9933 px |
| A2 | 420 × 594 mm | 42 × 59.4 cm | 16.54 × 23.39 in | 0.2495 m² | 4961 × 7016 px |
| A3 | 297 × 420 mm | 29.7 × 42 cm | 11.69 × 16.54 in | 0.1247 m² | 3508 × 4961 px |
| A4 | 210 × 297 mm | 21 × 29.7 cm | 8.27 × 11.69 in | 0.0624 m² | 2480 × 3508 px |
| A5 | 148 × 210 mm | 14.8 × 21 cm | 5.83 × 8.27 in | 0.0311 m² | 1748 × 2480 px |
| A6 | 105 × 148 mm | 10.5 × 14.8 cm | 4.13 × 5.83 in | 0.0155 m² | 1240 × 1748 px |
| A7 | 74 × 105 mm | 7.4 × 10.5 cm | 2.91 × 4.13 in | 0.0078 m² | 874 × 1240 px |
| A8 | 52 × 74 mm | 5.2 × 7.4 cm | 2.05 × 2.91 in | 0.0038 m² | 614 × 874 px |
| A9 | 37 × 52 mm | 3.7 × 5.2 cm | 1.46 × 2.05 in | 0.0019 m² | 437 × 614 px |
| A10 | 26 × 37 mm | 2.6 × 3.7 cm | 1.02 × 1.46 in | 0.001 m² | 307 × 437 px |
Dimensions are rounded down to whole millimetres, which is why A5 is 148 mm wide rather than exactly half of 297 mm. The standard also allows tolerances: ±1.5 mm up to 150 mm, ±2 mm up to 600 mm and ±3 mm above that.
The halving principle
The whole system rests on one rule. Fold an A sheet across the middle of its long side and you get the next size down, with exactly the same shape. One A0 sheet makes two A1, four A2, eight A3 and sixteen A4.
That only works with an aspect ratio of 1 to √2. Any other ratio makes the half narrower or wider than the original. In practice, a design made in A4 can be enlarged to A3 or reduced to A5 without distortion or white borders. A copier only needs two settings for this, 141 % and 71 %.
- One size up
- 141 % (exactly √2 = 1.414)
- One size down
- 71 % (exactly 1/√2 = 0.707)
- Two sizes up
- 200 % (for example A5 to A3)
- Two sizes down
- 50 %
The full table for every combination from A0 to A10 is on the scaling factor calculator.
What each A size is used for
| Size | Typical use |
|---|---|
| A0 | Architectural plans, technical drawings, large posters, conference posters |
| A1 | Posters, plans, pavement signs |
| A2 | Posters, wall calendars, sketch pads, notices |
| A3 | Drawings, small posters, spreadsheets, an open A4 brochure |
| A4 | Letters, forms, printouts, exercise books, ring binders |
| A5 | Flyers, notebooks, booklets, diaries |
| A6 | Postcards, index cards, roughly paperback size |
| A7 | Notepads, revision cards, small flyers, tickets |
| A8 to A10 | Labels, small stickers, mini notes, pieces on a press sheet |
The small sizes A8, A9 and A10
A8 measures 52 × 74 mm, a little smaller than a business card (85 × 55 mm in Europe), so it is not normally used for cards even though you sometimes read that it is. A9 (37 × 52 mm) and A10 (26 × 37 mm) are rare in everyday life. They turn up as labels, small stickers and as pieces on a press sheet when many small items are printed together. Full details are on the A8, A9 and A10 pages.
The oversizes 2A0 and 4A0
Above A0, the standard mentions two special sizes. 2A0 (1189 × 1682 mm) equals two A0 sheets side by side, 4A0 (1682 × 2378 mm) four of them. They are used for very large plans and posters and are not part of the series proper. More on the 2A0 and 4A0 pages.
Who invented the A series?
The series in its current form comes from the engineer Walter Porstmann and was published as DIN 476 on 18 August 1922. The 1 to √2 ratio itself is older: Georg Christoph Lichtenberg described it in a letter in 1786. The full story is on the history of paper sizes page.
Frequently asked questions
What is the largest A size?
In the series proper, A0 at 841 × 1189 mm. Above it there are the oversizes 2A0 and 4A0.
How big is A0 in square metres?
One square metre. Rounded to whole millimetres it is exactly 0.99995 m².
What percentage is A4 to A3?
Enlarge A4 to A3 at 141 %, reduce A3 to A4 at 71 %.
How many A4 pages fit on A3?
Exactly two, side by side.