Ever come across a document labeled as “A4” and wondered what that even means? If you’ve seen the term but aren’t sure what size it is or how it compares to U.S. paper sizes, don’t worry. This guide is here to help you understand A4 paper in the simplest way possible—even a 10-year-old could get it!
What Is A4 Paper, Anyway?
A4 paper is one of the most commonly used paper sizes in the world, especially outside the United States. It’s part of the international paper size system known as the ISO 216 standard, which includes a range of paper sizes labeled A0, A1, A2, all the way down to A10. The A4 paper specifically falls right in the middle of this series and is widely used for everyday printing, school assignments, office documents, and even personal letters.
You might think of A4 as just “regular paper” if you’re outside the U.S., because it’s the default size in most countries—including the UK, Australia, India, Germany, and many more. Even though the U.S. mostly uses “Letter size” (which is a little wider and shorter than A4), A4 paper is still available and often used here too, especially in international business, art, and design fields.
What Size Are A4 Paper in Inches and CM?
Now let’s get into the exact dimensions. A4 paper has a specific size that doesn’t change:
- In inches: 8.27 × 11.69 inches
- In centimeters (cm): 21 × 29.7 cm
- In millimeters (mm): 210 × 297 mm
It’s just slightly taller and a bit narrower than the U.S. Letter size, which is 8.5 × 11 inches. That tiny difference can matter a lot in design and formatting, especially when it comes to printing documents.
Quick Tip: Always check your printer settings before printing an A4-sized document in the U.S., as most default to “Letter” format.
A4 Paper Size Compared to Other Papers
So how does A4 size stack up against other common paper sizes? Let’s look at a few popular ones.
A4 vs Letter Size (U.S.)
- A4: 8.27 × 11.69 inches
- Letter: 8.5 × 11 inches
A4 paper is slightly narrower and a bit taller than U.S. Letter paper. While the difference seems small, it can affect margins, layout, and how much content fits on the page. If you’re dealing with international documents, it’s good to know the distinction.
A4 vs Legal Size
- A4: 8.27 × 11.69 inches
- Legal: 8.5 × 14 inches
Legal paper is much longer than A4. It’s commonly used for legal documents in the U.S., hence the name. If you’re printing something formal like contracts or court papers, you might see Legal paper in use, not A4.
A4 vs A5 Paper
- A4: 210 × 297 mm
- A5: 148 × 210 mm
A5 is exactly half the size of A4 when you fold it in half lengthwise. That’s why A5 is often used for booklets, notepads, or small flyers. The A-series sizes scale perfectly with each other, which is one of the best things about the ISO system.
Where Is A4 Paper Used Most?
A4 paper is the standard paper size in over 150 countries. That includes most of Europe, Asia, Africa, South America, and Oceania. Schools, governments, and businesses in these regions rely heavily on A4 for printing and documentation.
Even though the U.S. prefers Letter size, many international companies, embassies, and import/export businesses based in America still use A4, especially when communicating globally.
Here are a few everyday places where A4 paper is used:
- Office printers and copiers
- School homework and tests
- Flyers and brochures
- Business reports
- Personal printing (letters, resumes, etc.)
Why Is A4 Paper So Popular?
A4 paper is popular because of its perfect ratio and smart design. The ISO standard makes it easy to resize documents without losing proportions. For example, if you fold an A4 sheet in half, you get an A5 sheet. This means you can enlarge or reduce sizes without needing to adjust layouts too much.
Some reasons why A4 dominates globally:
- Fits most printers and copiers
- Easy to handle and carry
- International standard (ISO 216)
- Perfect size for writing and reading
- Scales naturally with other A-series sizes
It’s practical, it’s consistent, and it’s efficient.
Paper Size Chart for Quick Reference
Here’s a quick look at different paper sizes so you can compare them at a glance.
A-Series Paper Sizes
Paper SizeDimensions (mm)Dimensions (inches)
A0 841 × 1189 mm 33.1 × 46.8 in
A1 594 × 841 mm 23.4 × 33.1 in
A2 420 × 594 mm 16.5 × 23.4 in
A3 297 × 420 mm 11.7 × 16.5 in
A4 210 × 297 mm 8.3 × 11.7 in
A5 148 × 210 mm 5.8 × 8.3 in
A6 105 × 148 mm 4.1 × 5.8 in
Common Paper Sizes in USA
Paper SizeDimensions (inches)Used For
Letter 8.5 × 11 Standard U.S. printing
Legal 8.5 × 14 Contracts, legal documents
Tabloid 11 × 17 Posters, flyers
A4 Size in Pixels (For Screens)
If you’re designing digital documents or working with screen displays, here’s what A4 looks like in pixels:
DPI SettingA4 Size (pixels)
72 DPI 595 × 842 px
96 DPI 794 × 1123 px
150 DPI 1240 × 1754 px
300 DPI 2480 × 3508 px
These values are useful for digital designers, especially when creating PDFs, web printables, or digital stationery.
Can You Print A4 Paper in the USA?
Yes, you absolutely can! While most U.S. printers are set to Letter size by default, many home and office printers can handle A4 paper as well. All you need to do is adjust your print settings before printing. Most software like Microsoft Word, Google Docs, or Adobe Acrobat lets you pick the paper size before printing or saving your file.
Just make sure you:
- Change the printer paper setting to A4
- Use the right page setup on your document
- Double-check margins to avoid cutting off text
You can also buy A4 paper online or in office supply stores in the U.S. It’s not as common on shelves as Letter size, but it’s definitely available.
The Bottom Line
So, what size are A4 paper? Now you know—it’s 8.27 by 11.69 inches, or 21 by 29.7 centimeters, and it’s the world’s most commonly used paper size outside the U.S.
Whether you’re printing school assignments, reading international documents, or designing flyers, understanding A4 paper size gives you an edge. Even though the U.S. prefers Letter size, A4 is essential for global communication, printing, and design.
To sum it up:
- A4 is the go-to paper size in most countries
- It’s slightly taller and narrower than U.S. Letter size
- It’s perfect for printing, reading, and formatting
- And yes—you can definitely use it in the United States with a few quick adjustments
So next time you see “A4” on a document, you’ll know exactly what it means—and you’ll be ready to print it, share it, or design with it like a pro!
