A-Series Paper Size Dimensions Guide (in, cm, mm)
Measurements for International Paper Sizes & Envelope Dimensions
Have you ever opened a print menu or a new document template and paused at the list of paper sizes? Alongside the familiar “Letter” or “Legal,” you’ve likely seen options like “A4” or “A5” and wondered what they were for. These aren’t random codes or regional quirks; they are part of a beautifully resolved system—an international standard designed with an elegant simplicity that is easy to miss.
At 1-800 Office Solutions, we work with businesses every day that rely on consistent, accurate printing. Understanding how paper sizes are designed helps explain why your copier or multifunction printer behaves the way it does. This article reveals the clever logic behind these sizes and shows the genius built into a simple sheet of paper.
It’s Not Random—It’s a Masterclass in Systematic Design (ISO 216)
International paper sizes are governed by the ISO 216 standard, a masterclass in systematic design. This standard is broken down into three series, each designated by a letter: A, B, and C. Of these, the A-series is the most widely used for general printing and stationery, and it is built on one brilliant, foundational rule.
The entire system is created by halving. It starts with the largest sheet, A0, and every subsequent size is created by simply halving its predecessor along the longest side. An A1 sheet is half the size of an A0, an A2 is half the size of an A1, and so on. This single, clever constraint is what makes the entire system work, allowing everything from posters to business cards to scale perfectly while maintaining identical proportions.
A4 is the World’s Standard Letterhead
The cornerstone of this system, and the size you’re most likely to encounter, is A4. It serves as the standard letterhead for most of the world and is the most common application of the A-series’ elegant logic.
The most common of these sheet sizes is the international letterhead size A4, which measures 8-1/4 x 11-3/4 in, or 210 x 297 mm.
The table below shows how this scaling principle plays out, creating a predictable and harmonious family of sizes.
Standard International Paper Sizes and Measurements
| Paper Size | Inches | Millimeters | Centimeters |
|---|---|---|---|
| A0 | 33-1/8 x 46-13/16 in | 841 x 1188 mm | 84.1 x 118.8 cm |
| A1 | 23-3/8 x 33-1/8 in | 594 x 841 mm | 59.4 x 84.1 cm |
| A2 | 16-1/2 x 23-3/8 in | 420 x 594 mm | 42.0 x 59.4 cm |
| A3 | 11-3/4 x 16-1/2 in | 297 x 420 mm | 29.7 x 42.0 cm |
| A4 | 8-1/4 x 11-3/4 in | 210 x 297 mm | 21.0 x 29.7 cm |
| A5 | 5-7/8 x 8-1/4 in | 148 x 210 mm | 14.8 x 21.0 cm |
| A6 | 4-1/8 x 5-7/8 in | 105 x 148 mm | 10.5 x 14.8 cm |
| A7 | 2-15/16 x 4-1/8 in | 74 x 105 mm | 7.4 x 10.5 cm |
| A8 | 2-1/16 x 2-15/16 in | 52 x 74 mm | 5.2 x 7.4 cm |
The Envelopes Are Designed to Fit Perfectly
The true genius of the ISO 216 standard shines when you consider the C-series. This series is designed specifically for envelopes, with each size crafted to perfectly accommodate its corresponding A-series paper. This isn’t a happy accident; it’s a core feature of the system.
For example, a C4 envelope is perfectly sized to hold a flat A4 sheet. A C5 envelope holds a flat A5 sheet or, more commonly, an A4 sheet folded in half. A C6 holds an A6 sheet, or an A4 folded into quarters. And the familiar DL envelope, common for business correspondence, is designed to hold an A4 sheet folded into thirds. This thoughtful integration eliminates guesswork and ensures a professional fit every time.
Standard International Envelope Sizes and Measurements
| Size | Inches | Millimeters | Suitable Paper Formats |
|---|---|---|---|
| C4 | 12-3/4 x 9 in | 324 x 229 mm | Flat A4 or A3 folded once |
| C5 | 6-3/8 x 9 in | 162 x 229 mm | Flat A5, A4 folded once, or A3 folded twice |
| C6 | 4-1/2 x 6-3/8 in | 114 x 162 mm | Flat A6, A5 folded once, or A4 folded twice |
| C7/6 | 3-1/2 x 6-1/2 in | 89 x 165 mm | 1/3 A4 |
| DL | 4-1/4 x 8-5/8 in | 110 x 220 mm | A5 folded once or A4 folded twice |
Conclusion: Appreciating Simple Genius
The international paper standard is far more than a collection of arbitrary sizes. It is a beautifully resolved system where form and function align perfectly, and where papers and envelopes are designed to work together seamlessly. What at first appears to be a confusing code in a print menu is actually a powerful example of practical, user-focused design.
Now that you know the logic, what other invisible design standards in our daily lives have we been taking for granted?
