A4 Paper Size: Dimensions in mm, cm & Inches

A4 paper measures 210 × 297 millimeters, which works out to 21 × 29.7 centimeters or 8.27 × 11.69 inches. It is the standard paper size for offices, schools, and home printers in nearly every country in the world, defined by the international ISO 216 paper standard.

If you have ever printed a document only to find the margins cut off or a PDF that looks slightly stretched, a mismatch between A4 and US Letter paper is often to blame. This complete guide gives you the exact A4 dimensions in every unit of measurement, a quick conversion chart, the full A0 to A10 paper size series, pixel dimensions for designers, and side-by-side comparisons with US Letter paper and familiar everyday objects.

A4 Paper Size Conversion Chart

Dimension	Millimeters	Centimeters	Inches
Width	210 mm	21 cm	8.27 in
Height	297 mm	29.7 cm	11.69 in
Diagonal	363.7 mm	36.37 cm	14.32 in
Area	62,370 mm²	623.7 cm²	96.68 in²

1. A4 Paper Dimensions at a Glance

A4 is one of the most handled measurements in everyday life, yet surprisingly few people can quote its exact size from memory. Under ISO 216, the international paper size standard, A4 is defined as 210 millimeters wide and 297 millimeters tall in portrait orientation. Its aspect ratio is 1 to the square root of 2, or approximately 1:1.4142. That ratio is the clever secret behind the whole A-series: it is the only proportion that lets you cut or fold a sheet in half and end up with the exact same shape, just smaller. This property is why scaling a document between A sizes never stretches or squashes the layout.

The standard has deep roots. It began as the German DIN 476 specification in 1922, developed from the work of physicist Wilhelm Ostwald and engineer Walter Porstmann, and was later adopted internationally as ISO 216. Today A4 is the default paper size in every country that uses the metric system, which means just about the entire world. The main exceptions are the United States and Canada, where the slightly wider and shorter US Letter size (8.5 × 11 inches) rules offices and printers. If you buy a printer, a ream of paper, or a notebook almost anywhere outside North America, A4 is what you will get.

A single A4 sheet covers 623.7 square centimeters, exactly one-sixteenth of a square meter. Paper weight is measured in grams per square meter (gsm), so a standard 80 gsm A4 sheet weighs about 5 grams — sixteen sheets weigh roughly 80 grams, and a full ream of 500 sheets comes in at close to 2.5 kilograms. Here are the key facts in one place:

• Official size: 210 × 297 mm (ISO 216)
• Aspect ratio: 1 : √2 (1 : 1.4142)
• Area: 1/16 m² (623.7 cm²)
• Used in: all metric-system countries worldwide
• Orientation: portrait 210 × 297 mm, landscape 297 × 210 mm

2. A4 Size in Millimeters

The millimeter is the native unit of the ISO 216 standard, so 210 × 297 mm is the most exact way to state the A4 size. Every other unit — centimeters, inches, pixels — is derived from these two numbers. The dimensions look oddly unrounded, but there is an elegant reason: the series starts with A0, defined as one square meter in area with the 1:√2 aspect ratio, which gives 841 × 1189 mm. Each step down the series halves the longer side and rounds to the nearest millimeter, so A1 becomes 594 × 841 mm, A2 becomes 420 × 594 mm, A3 becomes 297 × 420 mm, and finally A4 lands on 210 × 297 mm.

In practice, tiny manufacturing tolerances mean a real sheet can vary by a fraction of a millimeter, and paper can swell or shrink slightly with humidity, but for printing, design, and everyday use, 210 × 297 mm is the figure to remember. If you are setting up a document in Word, InDesign, or Google Docs, entering these exact millimeter values guarantees your layout matches the physical page. Most design software outside North America defaults to A4, while US software defaults to Letter — one of the most common reasons documents reflow unexpectedly when shared internationally.

3. A4 Size in Centimeters

In centimeters, A4 measures 21 × 29.7 cm. The height of 29.7 cm is one of the most useful numbers to keep in mind, because it falls just 3 millimeters short of 30 centimeters. If you want an instant real-world sense of A4’s height, picture a standard 30 cm school ruler and shave off a sliver — that is your sheet of A4 standing upright. The width of 21 cm is a comfortable handful: noticeably wider than a paperback book page but narrower than a magazine.

Centimeters are the friendliest unit for measuring A4 by hand. Lay the sheet on a desk in portrait orientation and run a tape measure down the long edge — you should read 29.7 cm, and across the short edge exactly 21 cm. If your measurement is off by a millimeter or two, do not worry: paper can expand or contract slightly with humidity. If you are unsure how to read the markings, our guide on how to read a measuring tape walks through the process step by step.

4. A4 Size in Inches

In inches, A4 measures 8.27 × 11.69 inches. The conversion is simple division: one inch equals exactly 25.4 millimeters, so 210 ÷ 25.4 = 8.2677 inches wide and 297 ÷ 25.4 = 11.6929 inches tall, conventionally rounded to 8.27 × 11.69 in. These rounded figures are what you will see on packaging, printer trays, and paper specifications across the English-speaking world.

The height of 11.69 inches is worth remembering because it sits just under one foot (12 inches) — hold a sheet of A4 upright next to a 12-inch ruler and the paper comes up about a third of an inch short. The width of 8.27 inches is a little over two-thirds of a foot. If you work with imperial measurements regularly, our inches reference covers the conversions you will use most often, from fractions of an inch to feet and yards.

5. The Complete A-Series Size Chart: A0 to A10

A4 does not stand alone — it is one step in the A-series defined by ISO 216, which runs from the poster-sized A0 down to the stamp-sized A10. Each size is exactly half the area of the one before it. Here is the full chart with dimensions in millimeters and inches:

Size	Millimeters	Inches
A0	841 × 1189 mm	33.11 × 46.81 in
A1	594 × 841 mm	23.39 × 33.11 in
A2	420 × 594 mm	16.54 × 23.39 in
A3	297 × 420 mm	11.69 × 16.54 in
A4	210 × 297 mm	8.27 × 11.69 in
A5	148 × 210 mm	5.83 × 8.27 in
A6	105 × 148 mm	4.13 × 5.83 in
A7	74 × 105 mm	2.91 × 4.13 in
A8	52 × 74 mm	2.05 × 2.91 in
A9	37 × 52 mm	1.46 × 2.05 in
A10	26 × 37 mm	1.02 × 1.46 in

6. How the A-Series Halving Rule Works

The logic of the A-series is beautifully simple: every size is made by halving the sheet above it. Take an A3 sheet (297 × 420 mm) and cut it across the long side, and you get two A4 sheets (210 × 297 mm). Fold an A4 sheet in half and you get A5 (148 × 210 mm), the size of a typical paperback novel page or a half-sheet flyer. Keep going and you reach A6 (105 × 148 mm), the classic postcard size, then A7 and A8, and all the way down to A10 (26 × 37 mm), which is roughly the size of a postage stamp.

Going the other direction works the same way: two A4 sheets side by side make one A3, and two A3 sheets make one A2. The idea traces back to 1786, when German scientist Georg Christoph Lichtenberg observed that a rectangle with sides in the ratio 1:√2 keeps its proportions when halved. For anyone who prints booklets, posters, or flyers, this means you can scale a design from A4 to A3 or shrink it to A5 without stretching, squashing, or reflowing a single element. The layout simply grows or shrinks, which is why designers working to ISO standards rarely think twice about resizing.

7. A4 Paper Size in Pixels

For digital design, A4 must be translated into pixels, and the answer depends on the resolution (DPI) you are working at. The math is straightforward: multiply the inch dimensions by the DPI. At the print industry’s standard 300 DPI, A4 is 2480 × 3508 pixels (8.2677 × 300 = 2480, 11.6929 × 300 = 3508). At 150 DPI, often used for large-format drafts, it is 1240 × 1754 pixels. At 72 DPI, the old screen resolution, it is 595 × 842 pixels.

Note that pixel dimensions are always rounded to whole numbers, so you may see slightly different figures (such as 2480 × 3508 versus 2481 × 3508) depending on the software — both are correct within rounding. For crisp professional printing, always design at 300 DPI and export at the full 2480 × 3508 pixels. For web use or on-screen PDFs, 150 DPI is usually plenty and keeps file sizes manageable. If you are creating a full-bleed design with ink running to the paper’s edge, remember to add a 3 mm bleed on all sides, making your document 216 × 303 mm before trimming.

8. A4 vs US Letter: Key Differences

The most common point of confusion is US Letter, the North American standard at 8.5 × 11 inches (215.9 × 279.4 mm). Compared with A4, Letter is 5.9 mm wider but 17.6 mm shorter — close enough that the two look interchangeable at a glance, but different enough to cause real problems. Their aspect ratios differ (1:1.414 for A4 versus 1:1.294 for Letter), so a document laid out for one will not map cleanly onto the other: text reflows, margins shift, and printers may scale or crop the page.

The practical fix is simple: check your paper size setting before you print. In Word or Google Docs, set the page size to A4 when your paper tray holds A4, and to Letter when it holds Letter. If you receive a document formatted for the other size, use the “fit to page” or “scale to fit” option rather than printing at 100 percent. The table below puts A4 alongside the paper sizes you are most likely to encounter:

Paper size	Millimeters	Inches	Compared to A4
A3	297 × 420 mm	11.69 × 16.54 in	Twice the area of A4
A5	148 × 210 mm	5.83 × 8.27 in	Half the area of A4
US Letter	215.9 × 279.4 mm	8.5 × 11 in	Wider but shorter than A4
US Legal	215.9 × 355.6 mm	8.5 × 14 in	Same width as Letter, much taller
Tabloid / Ledger	279.4 × 431.8 mm	11 × 17 in	Twice the area of US Letter
B5 (JIS)	182 × 257 mm	7.17 × 10.12 in	Slightly smaller than A4
Executive	184.2 × 266.7 mm	7.25 × 10.5 in	Smaller than A4
Half Letter	139.7 × 215.9 mm	5.5 × 8.5 in	Half the area of US Letter

9. A4 Compared to Everyday Objects

Numbers on a chart are useful, but most people judge size by comparison. An A4 sheet is a familiar thing to hold: large enough to write a full page comfortably, small enough to slip into a bag or folder. Here is how it stacks up against objects you probably have within arm’s reach:

Object	Size	Comparison with A4
12-inch ruler	304.8 mm long	About 8 mm longer than A4’s height
US Letter sheet	215.9 × 279.4 mm	Slightly wider, slightly shorter
Standard clipboard	About 229 × 318 mm	A little larger all around
13-inch laptop screen	About 13 in diagonal	A4’s diagonal is larger at 14.3 in
Typical fashion magazine	About 203 × 279 mm	Slightly smaller than A4
Hardcover novel page	About 156 × 234 mm	Noticeably smaller than A4
Manila envelope (9 × 12 in)	About 229 × 305 mm	Slightly wider and taller

10. Common Uses for A4 Paper

A4 is the default canvas for an enormous range of documents. In offices it is the standard for letters, reports, contracts, invoices, and meeting agendas. Job seekers format résumés and CVs to A4, and academic life runs on it: essays, theses, worksheets, and exam papers are all A4 by default in metric-system countries. Marketing teams use it for flyers, brochures, price lists, and folded leaflets, while A4 notebooks, sketchpads, and printer paper fill store shelves worldwide. Architects and engineers print drawings on larger A-series sheets, but their everyday paperwork is A4. Even origami diagrams and paper craft templates usually assume A4, and most home printers sold outside North America come with their trays preset to it. Its ubiquity is self-reinforcing: because everything from folders to filing cabinets to printer trays is built around A4, A4 remains the obvious choice for the next document you create.

11. How to Measure A4 Paper Yourself

Verifying a sheet is A4 takes less than a minute. Place the paper on a flat surface in portrait orientation — the long edge vertical — and measure the short edge across the top: it should read 210 mm (21 cm). Then measure the long edge down the side: 297 mm (29.7 cm). A standard ruler or tape measure is all you need. If your sheet measures 8.5 × 11 inches instead, you are holding US Letter, not A4. Remember that paper is hygroscopic, meaning it absorbs moisture from the air and can swell or shrink by a fraction of a millimeter, so allow a tiny margin of error before declaring a sheet the wrong size. For a quick sanity check without any tools, fold the sheet in half: if the folded shape looks exactly like a smaller version of the original, the 1:√2 ratio is doing its job.

Frequently Asked Questions

What is the exact size of A4 paper in inches?

A4 paper is exactly 8.2677 × 11.6929 inches, conventionally rounded to 8.27 × 11.69 inches. The precise figures come from dividing the ISO 216 millimeter dimensions (210 × 297 mm) by 25.4, the exact number of millimeters in an inch.

Is A4 the same size as US Letter?

No. A4 (210 × 297 mm) is narrower but taller than US Letter (215.9 × 279.4 mm, or 8.5 × 11 in). The difference of about 6 mm in width and 18 mm in height is enough to shift margins and reflow text, so always match your document’s page size to the paper in your printer tray.

What paper size is half of A4?

Half of an A4 sheet is A5, which measures 148 × 210 mm (5.83 × 8.27 in). Thanks to the 1:√2 aspect ratio shared by the whole A-series, A5 has exactly the same shape as A4 — just half the area. A6 (105 × 148 mm), the classic postcard size, is half of A5.

How many pixels is A4 at 300 DPI?

At 300 DPI, the professional print standard, A4 is 2480 × 3508 pixels. At 150 DPI it is 1240 × 1754 pixels, and at 72 DPI it is 595 × 842 pixels. Always design print work at 300 DPI for crisp results, and remember that pixel figures are rounded to whole numbers.

Final Thoughts

A4 paper’s dimensions — 210 × 297 mm, 21 × 29.7 cm, or 8.27 × 11.69 inches — are worth memorizing because they show up everywhere: in your printer tray, your documents, and your notebooks. Its clever 1:√2 proportions make the whole A-series scale cleanly from poster-size A0 down to stamp-size A10, which is why the standard has endured for nearly a century. Just remember its North American cousin, US Letter, is a slightly different shape, so match your page setup to your paper before printing. Whether you are measuring by hand, designing at 300 DPI, or simply trying to buy the right ream, A4 is one measurement that pays to know exactly. Keep the conversion chart above bookmarked for quick reference, and the next time a document prints with odd margins, check the paper size first — it is the culprit more often than you would expect.