Paper Size Reference
Quick-reference tables for international, US, and photo paper sizes with dimensions in millimeters and inches.
| Size | Width (mm) | Height (mm) | Width (in) | Height (in) |
|---|---|---|---|---|
| A0 | 841 | 1189 | 33.11 | 46.81 |
| A1 | 594 | 841 | 23.39 | 33.11 |
| A2 | 420 | 594 | 16.54 | 23.39 |
| A3 | 297 | 420 | 11.69 | 16.54 |
| A4 | 210 | 297 | 8.27 | 11.69 |
| A5 | 148 | 210 | 5.83 | 8.27 |
| A6 | 105 | 148 | 4.13 | 5.83 |
| A7 | 74 | 105 | 2.91 | 4.13 |
A4 vs. US Letter
Letter is 6 mm wider but 18 mm shorter than A4. Documents designed for one may clip content when printed on the other.
The ISO A-Series Paper System
The ISO 216 standard defines the A-series paper sizes used by virtually every country except the United States and Canada. The system is elegantly designed: A0 has an area of exactly 1 square meter, and each subsequent size (A1, A2, A3, etc.) is created by folding the previous size in half parallel to the shorter side.
The key to the system is the aspect ratio of 1:√2 (approximately 1:1.414). This unique ratio means that when you fold the paper in half, the resulting half retains the same proportions. This allows documents to be scaled between any A size without distortion — a property called self-similar scaling. An A3 document can be reduced to A4 at 70.7% (1/√2) with no cropping or stretching.
A4 (210 × 297 mm) is the workhorse of the system — used for letters, documents, magazines, and forms in over 200 countries. It is the default paper size in every printer and word processor outside North America.
US Paper Sizes
The United States and Canada use their own paper size system, which predates the ISO standard. US Letter (8.5 × 11 inches) is the most common, used for business correspondence, printing, and photocopying. Legal (8.5 × 14 inches) is used for legal documents, contracts, and some government forms.
Unlike the ISO system, US paper sizes do not follow a mathematical pattern. This means scaling between sizes (Letter to Tabloid, for example) requires cropping or adding margins. The lack of a consistent aspect ratio is one reason many countries adopted the ISO system.
When sharing documents internationally, the A4-vs-Letter difference matters. A document designed for US Letter may have its bottom edge cut off when printed on A4 (which is 18 mm shorter), while an A4 document printed on Letter may have extra space on the sides but clipped content at the bottom.
Photo Print Sizes
Photo print sizes follow their own conventions, largely inherited from the photographic film era. The most common size, 4×6 inches (102 × 152 mm), matches the 2:3 aspect ratio of 35mm film and most digital camera sensors. Larger prints like 8×10 have a 4:5 ratio, which means some cropping is required when printing from a standard digital photo.
When ordering prints, always check the aspect ratio of your image against the print size. A 4:3 image (common from smartphones) printed at 4×6 (2:3 ratio) will need cropping on two sides. Most photo printing services let you choose between cropping and adding white borders.