A4 is the most widely used paper size in the world outside North America. Defined by the international ISO 216 standard, it serves as the default format for letters, official documents, magazines, and office printing across Europe, Asia, and most of the globe. Understanding its exact dimensions in centimetres, millimetres, and inches is essential for anyone involved in printing, design, or document preparation.
The ISO 216 standard organises A-series paper around a consistent √2 aspect ratio. This means that when you fold an A4 sheet in half parallel to its shorter edge, you get an A5 sheet with exactly the same proportions. The system allows seamless scaling between sizes without distortion, a feature that makes it invaluable for both digital and print workflows.
This guide provides the exact A4 dimensions in cm, mm, and inches, compares A4 with A5 and A2, explains pixel conversions for digital design, and covers the landscape orientation. All figures are drawn from established sources including the ISO 216 standard, manufacturer data, and international reference tables.
What are the exact A4 paper dimensions in cm, mm, and inches?
The official dimensions of A4 paper, as specified by ISO 216, are 210 mm by 297 mm. In centimetres, that is 21.0 cm by 29.7 cm. In inches, the measurement is 8.27 in by 11.69 in, though some sources round this to 8.3 in by 11.7 in depending on the level of precision required.
21.0 x 29.7 cm
210 x 297 mm
8.27 x 11.69 in
2480 x 3508 px
Multiple authoritative sources confirm these values. Papersizes.org lists A4 as 210 × 297 mm with an inch conversion of 8.3 × 11.7. Papersizes.io reports 210 × 297 mm and 8.27 × 11.69 inches. A4-size.com gives the inches as 8.268 × 11.693. Wikipedia also records 210 × 297 mm and notes the comparison with US Letter (216 × 279 mm). The minor differences in inch values are simply due to rounding: 1 inch equals exactly 25.4 mm, so 210 mm ÷ 25.4 = 8.2677 in and 297 mm ÷ 25.4 = 11.6929 in.
- A4 is the standard paper size globally except in North America, where Letter size is used.
- The aspect ratio of A4 is 1:√2 (approximately 1:1.4142), enabling easy scaling between A sizes.
- Cutting an A4 sheet in half parallel to its shorter edge produces an A5 sheet.
- A4 is defined by the ISO 216 standard, first adopted internationally in 1975.
- The surface area of an A4 sheet is 623.7 cm² (0.06237 m²).
- A4 paper fits unfolded inside a standard C4 envelope.
- The official tolerance for machine-cut A4 paper is ±1.5–2 mm.
| Unit | Value |
|---|---|
| Centimetres (cm) | 21.0 x 29.7 cm |
| Millimetres (mm) | 210 x 297 mm |
| Inches (in) | 8.27 x 11.69 in |
| Feet (ft) | 0.69 x 0.97 ft |
| Pixels (72 DPI) | 595 x 842 px |
| Pixels (300 DPI) | 2480 x 3508 px |
| Aspect Ratio | 1:1.414 (√2) |
How does A4 compare to A5 and A2 sizes?
The A-series paper system is built on a simple halving principle. A0 has an area of exactly 1 m², and each subsequent size halves that area while preserving the √2 aspect ratio. This makes comparisons between A4, A5, and A2 straightforward and predictable.
What is A5 size in cm?
A5 paper measures 148 mm by 210 mm, which converts to 14.8 cm by 21.0 cm. In inches, it is 5.83 by 8.27. Because A5 is exactly half the area of A4, it is popular for notebooks, flyers, pocket-sized booklets, and inserts. Two A5 sheets placed side by side match the dimensions of one A4 sheet.
What is A2 size in cm?
A2 paper measures 420 mm by 594 mm, or 42.0 cm by 59.4 cm. Its inch equivalent is 16.54 by 23.39. A2 has four times the area of A4, making it a common choice for posters, architectural drawings, and large-format displays. Two A3 sheets (each twice the size of A4) combine to form a single A2 sheet.
For everyday reference: A4 is the size of a standard letter or magazine page. A5 is half that — a typical notepad or paperback book. A2 is four times larger than A4 and is used for posters and signage. The halving relationship means that folding an A2 sheet twice yields an A4 sheet.
How does A4 compare to US Letter size?
US Letter paper measures 215.9 mm by 279.4 mm (8.5 by 11 inches). A4 is 6 mm narrower and 18 mm taller. This difference may not seem large, but it can cause layout problems when documents designed for one standard are printed on the other. Most modern software handles the adjustment automatically, but for critical print jobs it is wise to check the target paper size beforehand.
| Size | mm (Width × Height) | cm (Width × Height) | Inches (Width × Height) | Area (cm²) |
|---|---|---|---|---|
| A2 | 420 × 594 | 42.0 × 59.4 | 16.5 × 23.4 | 2494.8 |
| A3 | 297 × 420 | 29.7 × 42.0 | 11.7 × 16.5 | 1247.4 |
| A4 | 210 × 297 | 21.0 × 29.7 | 8.3 × 11.7 | 623.7 |
| A5 | 148 × 210 | 14.8 × 21.0 | 5.8 × 8.3 | 311.85 |
| A6 | 105 × 148 | 10.5 × 14.8 | 4.1 × 5.8 | 155.4 |
What is A4 size in pixels for digital design?
Pixel dimensions for A4 are not fixed — they depend entirely on the resolution (DPI) at which the document is rendered or printed. For web and screen use, 72 DPI is the traditional standard. For high-quality printing, 300 DPI is the norm.
What is A4 resolution at 300 DPI?
At 300 DPI, the most common print resolution, an A4 document without bleed measures 2480 pixels by 3508 pixels. If you need a 3 mm bleed for professional printing, the dimensions increase to 2551 by 3579 pixels. These figures come from instantprint.co.uk, a commercial printing resource.
What is A4 size in pixels at 72 DPI?
At 72 DPI, the typical screen resolution, A4 measures approximately 595 pixels by 842 pixels. This is suitable for on-screen previews, digital documents, and web graphics. At 150 DPI, a common mid-range resolution, A4 is 1240 by 1754 pixels.
| DPI | Pixels (Width × Height, no bleed) |
|---|---|
| 72 | 595 × 842 |
| 150 | 1240 × 1754 |
| 300 | 2480 × 3508 |
What is A4 landscape size, and how does it differ from portrait?
Orientation simply swaps the width and height dimensions. In portrait mode, A4 measures 21.0 cm wide by 29.7 cm tall. In landscape mode, the dimensions become 29.7 cm wide by 21.0 cm tall. The paper itself does not change — only the direction in which it is used.
A4 landscape in cm: 29.7 cm (width) × 21.0 cm (height). In inches: 11.69 × 8.27. In mm: 297 × 210. The pixel values at 300 DPI become 3508 × 2480 instead of the portrait 2480 × 3508.
Landscape orientation is commonly used for presentations, wide-format tables, brochures, and any layout where horizontal width is more important than vertical height. The ISO 216 standard does not mandate an orientation — it simply defines the sheet dimensions. Both portrait and landscape are valid uses of the same physical paper.
When switching between portrait and landscape, always verify that your document software is set to the correct orientation before exporting or printing. A common mistake is to design in landscape but print on portrait-oriented paper, which can lead to clipped margins and layout errors.
How did the A4 paper standard develop over time?
The history of the A4 format begins in early 20th-century Germany and culminated in a global standard that now governs paper sizes across most of the world.
- 1922 — The DIN 476 standard is introduced in Germany, defining the A, B, and C series of paper sizes. This is the direct precursor to the modern A4 format.
- 1975 — The ISO 216 standard is adopted internationally, based on DIN 476. It formalises the A4 dimensions of 210 × 297 mm and establishes the √2 aspect ratio as the core design principle.
- Present — A4 is the dominant paper size worldwide, used for letters, documents, printing, and official forms in every country except the United States and Canada, where ANSI/ASME Letter standards remain in place.
The ISO 216 standard also specifies tolerances: ±1.5 mm for dimensions up to 150 mm and ±2 mm for dimensions above 150 mm, ensuring consistent production quality across manufacturers. Extensions such as 2A0 and 4A0 exist for oversize printing, as noted in a University of Delaware Library guide.
How accurate are A4 paper dimensions across different units?
The core A4 dimensions are precisely defined by ISO 216 and are not subject to interpretation. The values 210 mm × 297 mm and 21.0 cm × 29.7 cm are exact. The inch equivalent, 8.27 × 11.69, is a rounding of the precise conversion (8.2677 × 11.6929). Pixel conversions, however, depend on the chosen DPI and are rounded to the nearest integer, which can cause very slight variations between software applications.
| Established information | Information that remains unclear |
|---|---|
| A4 is exactly 210 × 297 mm per ISO 216. | Pixel dimensions vary by DPI and rounding method — different software may report slightly different values. |
| 21.0 × 29.7 cm is the exact metric conversion. | Inch values are shown as 8.27 × 11.69 or 8.3 × 11.7 depending on rounding preference. |
| 300 DPI pixel dimensions (2480 × 3508) are standard for print without bleed. | With bleed, values change (e.g., 2551 × 3579 for 3 mm bleed), and these can differ by print shop. |
| The √2 aspect ratio is mathematically fixed. | No uncertainty exists in the aspect ratio itself — it is an exact geometric property. |
Why does A4 size matter for everyday use?
A4 is the default paper size for letters, forms, magazines, and office documents in most countries outside North America. Its 1:√2 aspect ratio means that when a sheet is cut in half parallel to its shorter side, the resulting smaller sheet retains the same proportions. This makes it an elegant and functional standard for design and document management. Designers, printers, and office workers rely on this consistency every day.
The difference between A4 and US Letter becomes significant in international contexts. A4 is 6 mm narrower but 18 mm longer than Letter (215.9 × 279.4 mm). A document formatted for Letter may have content clipped or misaligned when printed on A4, and vice versa. For anyone working across both standards, checking the paper size setting before printing is essential.
What do official sources say about A4 dimensions?
The ISO 216 standard itself states that A4 paper measures 210 mm × 297 mm. Adobe, in its Creative Cloud guide, notes that “the international letterhead A4 paper size is 21 x 29.7 cm, as defined by the ISO 216 standard.” Neenah Paper, a major manufacturer, documents A4 as 8-1/4 x 11-3/4 in, 210 x 297 mm, and 21.0 x 29.7 cm.
“A4 paper measures 210 mm × 297 mm.”
— ISO 216 Standard
“The international letterhead A4 paper size is 21 x 29.7 cm, as defined by the ISO 216 standard.”
— Adobe (Creative Cloud)
“A4: 8-1/4 x 11-3/4 in, 210 x 297 mm, 21.0 x 29.7 cm.”
— Neenah Paper
What is the key takeaway about A4 size?
A4 paper measures exactly 21.0 cm by 29.7 cm (210 mm by 297 mm), with an inch equivalent of 8.27 by 11.69. It is the backbone of international document standards, supported by the ISO 216 system, and its √2 aspect ratio allows seamless scaling across the entire A-series range. Whether you are printing a letter, designing a digital document, or choosing paper for a specific project, these dimensions provide a reliable and universal reference. For additional measurement conversions, see our 30 Inches in CM – Exact 76.2 cm Conversion Guide and our Standard Double Bed Size: UK, Ireland, cm, Feet Guide.
Frequently asked questions about A4 size
What is A4 size in inches exactly?
Exactly 8.2677 x 11.6929 inches, commonly rounded to 8.27 x 11.69 inches.
What is A4 size in feet?
Approximately 0.689 x 0.974 feet.
What is A4 landscape size in cm?
A4 landscape orientation is 29.7 cm (width) x 21.0 cm (height).
Is A4 the same as US Letter?
No. A4 is slightly narrower and longer than US Letter.
What size is A5 paper in cm?
A5 is 14.8 x 21.0 cm.
What size is A2 paper in cm?
A2 is 42.0 x 59.4 cm.
What is A4 size in pixels at 300 DPI?
2480 x 3508 pixels at 300 DPI without bleed.
What is the aspect ratio of A4?
The aspect ratio is 1:√2, approximately 1:1.4142.
Does A4 fit in a C4 envelope?
Yes, A4 fits unfolded inside a standard C4 envelope.
Why is A4 used globally instead of US Letter?
A4 is part of the ISO 216 standard based on the metric system and the √2 aspect ratio, adopted by most countries outside North America.
Amelia Foster is Business & Economy Correspondent at TheUKDaily.uk, covering the UK economy, markets, employment, household costs and consumer finance.