A Series Paper Sizes: A0 to A10 in Inches, MM & CM
A4 paper measures exactly 210 x 297 mm (8.27 x 11.69 inches), and it is the most widely used paper size in the world. The complete A series defined by ISO 216 ranges from A0 (841 x 1189 mm) down to A10 (26 x 37 mm), with each size being exactly half the area of the one before it. Below is the full reference table with every A size in millimeters, centimeters, inches, and the pixel dimensions needed for 300 DPI printing.
Complete A Series Paper Size Chart (A0-A10)
| Size | MM (W x H) | CM (W x H) | Inches (W x H) | Pixels @ 300 DPI | Area (m2) |
|---|---|---|---|---|---|
| A0 | 841 x 1189 | 84.1 x 118.9 | 33.11 x 46.81 | 9933 x 14043 | 1.0000 |
| A1 | 594 x 841 | 59.4 x 84.1 | 23.39 x 33.11 | 7016 x 9933 | 0.5000 |
| A2 | 420 x 594 | 42.0 x 59.4 | 16.54 x 23.39 | 4961 x 7016 | 0.2494 |
| A3 | 297 x 420 | 29.7 x 42.0 | 11.69 x 16.54 | 3508 x 4961 | 0.1247 |
| A4 | 210 x 297 | 21.0 x 29.7 | 8.27 x 11.69 | 2480 x 3508 | 0.0624 |
| A5 | 148 x 210 | 14.8 x 21.0 | 5.83 x 8.27 | 1748 x 2480 | 0.0311 |
| A6 | 105 x 148 | 10.5 x 14.8 | 4.13 x 5.83 | 1240 x 1748 | 0.0155 |
| A7 | 74 x 105 | 7.4 x 10.5 | 2.91 x 4.13 | 874 x 1240 | 0.0078 |
| A8 | 52 x 74 | 5.2 x 7.4 | 2.05 x 2.91 | 614 x 874 | 0.0038 |
| A9 | 37 x 52 | 3.7 x 5.2 | 1.46 x 2.05 | 437 x 614 | 0.0019 |
| A10 | 26 x 37 | 2.6 x 3.7 | 1.02 x 1.46 | 307 x 437 | 0.0010 |
All dimensions are per ISO 216. The mm values are the definitive standard; cm and inch values are derived conversions. For individual size detail pages, see A4 in inches, A3 in inches, A5 in inches, and A1 in inches.
How the ISO 216 System Works
The A series paper sizing system is built on two mathematical principles:
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A0 has an area of exactly 1 square meter. The dimensions of A0 (841 x 1189 mm) yield an area of 999,949 mm2, which rounds to 1 m2 within manufacturing tolerances.
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The aspect ratio is 1:sqrt(2) (approximately 1:1.4142). This specific ratio has a unique property: when you cut a sheet in half along its longer side, the two resulting halves have the same aspect ratio as the original. This means A1 is half of A0, A2 is half of A1, and so on, all the way down to A10, and every size in the series is geometrically similar.
The Halving Rule
Each A size is derived by halving the longer dimension of the previous size and swapping the width and height:
- A0: 841 x 1189 mm
- A1: 594 x 841 mm (1189 / 2 = 594.5, rounded to 594)
- A2: 420 x 594 mm (841 / 2 = 420.5, rounded to 420)
- A3: 297 x 420 mm (594 / 2 = 297)
- A4: 210 x 297 mm (420 / 2 = 210)
The ISO standard specifies that dimensions are rounded down to the nearest millimeter. This means there is a tiny area loss at each step, but the ratio remains consistent within practical tolerances.
Most Common A Sizes Explained
A4 (210 x 297 mm / 8.27 x 11.69 inches)
A4 is the global default paper size for office documents, letters, contracts, academic papers, and general printing. It is the standard in every country except the United States and Canada (which use US Letter size). Most printers, copiers, and multifunction devices worldwide are configured for A4 by default.
Common A4 uses: business letters, resumes, reports, invoices, forms, academic papers, and general office documents.
A3 (297 x 420 mm / 11.69 x 16.54 inches)
A3 is exactly double the size of A4. It is the standard size for architectural drawings at reduced scale, engineering diagrams, large spreadsheets, newspaper tabloid pages, and small posters. Many office laser printers support A3 printing, making it the largest commonly available size in office environments.
Common A3 uses: technical drawings, charts, small posters, menus, newspaper pages, and two-up A4 layouts.
A5 (148 x 210 mm / 5.83 x 8.27 inches)
A5 is half of A4 and is the most common size for notebooks, booklets, and flyers. It is widely used in publishing for pocket-sized books, event programs, and promotional handouts. Many commercial printers offer A5 booklet printing as a standard option.
Common A5 uses: notebooks, booklets, flyers, planners, pocket books, and event programs.
A6 (105 x 148 mm / 4.13 x 5.83 inches)
A6 is the international standard postcard size. It is also used for small flyers, invitation cards, and pocket-sized reference cards. A6 is exactly one quarter of an A4 sheet.
Common A6 uses: postcards, invitation cards, small flyers, and pocket reference cards.
A0 and A1 (Large Format)
A0 (841 x 1189 mm) and A1 (594 x 841 mm) are used for technical drawings, architectural plans, scientific posters, and large-format printing. A0 is the standard size for academic conference posters in many European institutions. Both sizes require wide-format printers or plotters.
A Series vs US Paper Sizes
The United States and Canada use a separate paper size system that is not based on ISO 216. The most relevant comparison is between A4 and US Letter, since these are the two dominant document sizes worldwide.
| ISO A Size | MM (W x H) | US Equivalent | MM (W x H) | Difference |
|---|---|---|---|---|
| A4 | 210 x 297 | Letter | 216 x 279 | Letter is 6 mm wider, 18 mm shorter |
| A3 | 297 x 420 | Tabloid (11x17) | 279 x 432 | Tabloid is 18 mm narrower, 12 mm taller |
| A5 | 148 x 210 | Half Letter | 140 x 216 | Half Letter is 8 mm narrower, 6 mm taller |
| A2 | 420 x 594 | C (17x22) | 432 x 559 | ANSI C is 12 mm wider, 35 mm shorter |
| A1 | 594 x 841 | D (22x34) | 559 x 864 | ANSI D is 35 mm narrower, 23 mm taller |
| A0 | 841 x 1189 | E (34x44) | 864 x 1118 | ANSI E is 23 mm wider, 71 mm shorter |
The key practical difference: documents designed for A4 may not print correctly on US Letter paper, and vice versa. A4 content can be clipped at the bottom when printed on Letter (which is shorter), and Letter content may have excessive bottom margins on A4 (which is taller). Always check your printer settings and document page size when exchanging files between regions.
For a detailed comparison, see our Letter vs A4 guide. For a complete reference of US paper dimensions, see US paper sizes.
A Series and C Series Envelopes
The ISO 269 standard defines C series envelope sizes specifically designed to hold A series paper. Each C envelope fits the corresponding A paper unfolded, and also fits the next larger A paper folded once.
| Envelope | MM (W x H) | Fits Unfolded | Fits Folded Once |
|---|---|---|---|
| C3 | 324 x 458 | A3 | A2 |
| C4 | 229 x 324 | A4 | A3 |
| C5 | 162 x 229 | A5 | A4 |
| C6 | 114 x 162 | A6 | A5 |
| C7 | 81 x 114 | A7 | A6 |
| C8 | 57 x 81 | A8 | A7 |
There is also a DL envelope (110 x 220 mm), which is the most common business envelope size. It fits A4 paper folded into thirds and is the standard for mailing letters and invoices in A4 countries.
How It Works
The C series dimensions are the geometric mean of the corresponding A and B series sizes. This ensures that each C envelope is slightly larger than the A paper it holds, providing enough clearance for easy insertion without excessive slack.
Resolution Requirements for Printing A Sizes
When preparing digital artwork or documents for print on A series paper, the required pixel dimensions depend on the target DPI. The table below shows the three most common DPI settings.
| Size | Pixels @ 150 DPI | Pixels @ 300 DPI | Pixels @ 600 DPI |
|---|---|---|---|
| A0 | 4967 x 7022 | 9933 x 14043 | 19866 x 28087 |
| A1 | 3508 x 4967 | 7016 x 9933 | 14031 x 19866 |
| A2 | 2480 x 3508 | 4961 x 7016 | 9921 x 14031 |
| A3 | 1754 x 2480 | 3508 x 4961 | 7016 x 9921 |
| A4 | 1240 x 1754 | 2480 x 3508 | 4961 x 7016 |
| A5 | 874 x 1240 | 1748 x 2480 | 3496 x 4961 |
| A6 | 620 x 874 | 1240 x 1748 | 2480 x 3496 |
- 150 DPI: Acceptable for large-format posters (A0, A1) viewed from several feet away.
- 300 DPI: The standard for commercial printing, office documents, and any print viewed at arm’s length.
- 600 DPI: Used for fine art reproduction, detailed technical drawings, and archival printing.
Use our DPI calculator to compute exact pixel requirements for any custom dimension.
Practical Tips for Working with A Sizes
Scaling Between Sizes
Because all A sizes share the same aspect ratio, scaling between them is straightforward:
- A4 to A3: Scale to 141% (or sqrt(2) x 100)
- A4 to A5: Scale to 71% (or 100 / sqrt(2))
- A3 to A1: Scale to 200% (two steps up = 2x)
- A4 to A0: Scale to 400% (four steps up = 4x)
When scaling multi-step (e.g., A4 to A1), multiply by 141% for each step or use the shortcut: each two-step jump doubles the scale factor.
Printer Margins
Most desktop printers cannot print to the edge of the paper. Typical non-printable margins are:
- Inkjet printers: 3-5 mm on each side
- Laser printers: 4-6 mm on each side
- Borderless inkjet printers: 0 mm (requires borderless-capable printer and correct paper size setting)
When designing documents for A series paper, set your safe content area at least 10 mm inside the paper edge to ensure nothing is clipped across different printer models.
Weight and Thickness
A series paper sizes specify only dimensions, not weight or thickness. Paper weight is measured separately in grams per square meter (gsm). Common weights:
| Weight (gsm) | Typical Use |
|---|---|
| 75-80 | Standard office/copy paper |
| 90-100 | Premium letterhead, forms |
| 120-150 | Brochures, covers, card inserts |
| 170-200 | Business cards (A8 cut), postcards |
| 250-350 | Thick card stock, book covers |
Because A0 has an area of 1 m2, the gsm rating directly tells you the weight of a single A0 sheet. For example, 80 gsm paper means one A0 sheet weighs 80 grams, one A1 sheet weighs 40 grams, one A4 sheet weighs 5 grams.
Frequently Asked Questions
What is A4 size in inches?
A4 paper is 210 x 297 mm, which equals 8.27 x 11.69 inches. It is the international standard for documents, letters, and office printing, used in every country except the US and Canada.
What is the difference between A4 and US Letter paper?
A4 is 210 x 297 mm (8.27 x 11.69 inches) while US Letter is 216 x 279 mm (8.5 x 11 inches). Letter is slightly wider but shorter than A4. This difference can cause formatting and margin issues when printing documents designed for the other size.
How does the A series paper sizing system work?
The A series is based on ISO 216. A0 has an area of exactly 1 square meter. Each subsequent size (A1, A2, A3, etc.) is created by cutting the previous size in half along its longer side. All sizes maintain the same 1:1.414 aspect ratio (1 to the square root of 2).
What are the most commonly used A paper sizes?
A4 (210x297 mm) is the most widely used size globally for office documents, letters, and forms. A3 (297x420 mm) is common for diagrams, charts, and small posters. A5 (148x210 mm) is used for notebooks, booklets, and flyers. A6 (105x148 mm) is the standard postcard size.
Which C series envelope fits which A paper size?
Each C series envelope is designed to fit the corresponding A size: C4 (229x324 mm) fits A4 unfolded, C5 (162x229 mm) fits A4 folded once or A5 unfolded, C6 (114x162 mm) fits A4 folded twice or A6 unfolded, and C3 (324x458 mm) fits A3 unfolded.