A4 Paper Size: 21 × 29.7 cm (8.27 × 11.69 in) | A4 vs Letter, Pixels and Inches

A4 paper is 21 × 29.7 cm, or 8.27 × 11.69 inches.

Most people looking up the A4 size already know what A4 paper looks like. Outside North America it is the everyday copy paper. What they need is the exact number: to set up a page layout, to work out pixel dimensions, to check whether a sheet will fit in a folder or envelope, or to figure out why a document sent from abroad printed with its margins cut off.

Here are the numbers people ask for most:

How big is A4? Quick reference (cm, mm, inches, pixels)

The area is about 623.7 square centimeters, and the aspect ratio is 1 : 1.414, or 1 : √2. That ratio is the heart of the whole A series, and the next section explains why it is so useful.

How the A series works: fold it in half and the shape stays the same

The A series (ISO 216) starts from A0, a sheet with an area of exactly one square meter (84.1 × 118.9 cm). Every time you fold a sheet in half, the number goes up by one:

Because the aspect ratio is fixed at √2, folding a sheet in half leaves its proportions unchanged. An A4 document reduced to A5 or enlarged to A3 keeps exactly the same shape. Most other paper systems in the world cannot do this, and it is the reason the A series dominates photocopiers.

For A5 from the angle of notebooks and planners, see A5 Paper Size. A6, a close relative of the postcard, has its own page: A6 Paper Size. Going up in size, each member of the family also has a dedicated guide: A3 Paper Size (two A4 sheets side by side), A2 Size, A1 Size, and all the way up to the origin of the series, A0 Paper Size.

The most common trap: A4 is not the world’s only standard sheet

In the United States, Canada, Mexico, the Philippines and a few other places, the default paper size is Letter, not A4:

Letter is about 6 mm wider than A4 and almost 2 cm shorter, a squatter version of A4. When documents travel between the two systems and are printed as is, the result is content cut off at the edges, layouts that shift, and footers that disappear. The fix is simple: before printing, choose “Fit to page” (or “Scale to fit paper”), or change the paper size in the document settings to match the printer’s paper. Legal shares Letter’s width but is much longer, so a Legal document printed on A4 needs to be scaled down as well.

How many pixels is A4?

To turn an A4 page into an image file or prepare it for print, the conversion formula is: millimeters ÷ 25.4 × DPI.

The 72 DPI figures come with a bit of trivia: PDF files measure pages in points (1 pt = 1/72 inch), so an A4 PDF page is 595 × 842 pt, exactly the same numbers as the pixel dimensions at 72 DPI.

How the A4 pixel numbers are calculated

Every pixel figure for A4 comes from the same steps: divide millimeters by 25.4 to get inches, multiply by the DPI, then round to a whole pixel. At 300 DPI, the width is 210 ÷ 25.4 × 300 = 2480.3, which becomes 2480, and the height is 297 ÷ 25.4 × 300 = 3507.9, which becomes 3508. At 600 DPI the results are 4960.6 × 7015.7, rounded to 4961 × 7016.

Because the A series is designed in metric units, its inch values always have decimals, so different software and websites sometimes disagree by one pixel. For example, 600 DPI is also often written as 4960 × 7016, depending on whether the decimal is truncated or rounded. A one-pixel difference has no visible effect on a print.

Use 300 DPI for print; for screens, only the pixel count matters

When you send a file to a printer or print shop, the standard is 300 DPI at actual size, which for A4 is 2480 × 3508 px. That is the baseline used across the printing industry. 600 DPI is only needed for scanning text and line art or for fine-art prints, and ordinary printed materials do not need it.

If the page will only be viewed on a screen (in a presentation, on a web page or on a phone), the DPI number does not affect sharpness at all, because screens only care about the total pixel count. The traditional convention is the 72 DPI set, 595 × 842 px. If people will zoom in on a phone or high-resolution display, the 150 DPI set, 1240 × 1754 px, is more than enough.

A4 compared with other common sizes

• A4 vs B5 (notebooks): the JIS B5 size used for many notebooks is 18.2 × 25.7 cm, and A4 is roughly a third larger in area. A notebook described as “a size smaller than A4” is usually B5.
• A4 vs a 4 × 6 photo: a 4 × 6 in print (10.16 × 15.24 cm) is about a quarter of the area of A4, and one sheet of A4 photo paper fits two 4 × 6 prints side by side, or three with a tighter layout (two portrait plus one landscape). See 4 × 6 Photo Size in Centimeters for details.
• A4 folded vs a postcard: A4 folded once (A5) is still larger than a postcard. Fold it again and you get A6 (10.5 × 14.8 cm), which is postcard-sized and close to the 4 × 6 in cards common in the US. For postcard rules by country, see the Postcard Size Guide.
• A4 vs a copy of an ID card: driver’s licenses, credit cards and most national ID cards use the ISO/IEC 7810 ID-1 size of 8.56 × 5.4 cm, so the front and back fit on a single A4 sheet with plenty of room to spare. For the card sizes themselves, see Credit Card and ID Card Size.

Frequently asked questions

How many centimeters is A4?

21 × 29.7 cm, or 210 × 297 mm. This is the ISO 216 international standard, and copy paper is this size everywhere in the world except a few countries in the Americas.

What is the aspect ratio of A4?

1 : 1.414, or 1 : √2. 29.7 ÷ 21 ≈ 1.414. The entire A series uses this ratio, so A4 can be reduced to A5 or enlarged to A3 without distortion.

What is A4 in inches?

About 8.27 × 11.69 inches. It is not a whole number of inches, because the A series was designed in metric units, so converting it to inches always produces decimals.

How many pixels is A4?

It depends on the resolution: 2480 × 3508 px at 300 DPI (the print standard), 1240 × 1754 px at 150 DPI, and 595 × 842 px at 72 DPI. For anything you plan to print, start at 300 DPI.

What size is A4 folded in half?

A5 (14.8 × 21 cm). Fold it again and you get A6 (10.5 × 14.8 cm). Every fold adds one to the number while the ratio stays at √2, which is the cleverest part of the A-series design.

What is the difference between A4 and Letter?

Letter is the US standard, 21.6 × 27.9 cm (8.5 × 11 in). It is about 6 mm wider and about 18 mm shorter than A4. The United States and Canada use Letter by default, so documents exchanged across borders often print with shifted layouts because of this difference. Check the paper setting before you print.

Which is bigger, A4 or B5?

A4. The JIS B5 size common for notebooks is 18.2 × 25.7 cm, and A4 is roughly a third larger in area. A notebook described as “a size smaller than A4” is usually B5.

How many pixels is A4 at 600 DPI?

4961 × 7016 px. The calculation is 210 ÷ 25.4 × 600 = 4960.6 and 297 ÷ 25.4 × 600 = 7015.7, rounded to whole numbers. For ordinary printing, 300 DPI (2480 × 3508 px) is enough; 600 DPI is mostly used for scanning text and line art or for fine-art output.

Keywords: A4 paper size, A4 size in cm, A4 size in inches, A4 dimensions, A4 in pixels, A4 vs Letter