Paper Sizes Explained - JetPens

Understanding International Paper Sizes

Most countries outside of North America use paper that fall into one of two series: A or B. Their measurements are defined by ISO 216, which was put together by the International Organization for Standardization.

A sizes are more common than B sizes, so we’ll start there.

A Series The A series and the measurements for each size in the series are shown above. Introduced in Germany during the 1920s, the A series quickly spread throughout Europe. By the 1970s, it was widely used throughout the world.

The first and largest A size is A0, which is 33.1 x 46.8 inches and has an area of one square meter. To create the next size, the previous size is cut in half horizontally. The resulting A1 size paper is 23.4 x 33.1 inches.

Due to a unique property of its aspect ratio, an A5 notebook is half the size of an A4 notebook. In most cases, cutting a paper in half would create two pieces with completely different proportions. But the A series uses an aspect ratio—the ratio of its width to its length—of 1:√2. When the paper is folded or cut in half horizontally, the two halves will have the same 1:√2 aspect ratio (approximately 1:1.4).

In countries that use the A series, the standard paper size is A4. At 8.3 x 11.7 inches, A4 paper is slightly longer and narrower than Letter size.

B Series The B series and the measurements for each size in the series are shown above. The B series is based on the same ideas as the A series. It also has an aspect ratio of 1:√2, and each size is half as large as the next size.

The main difference is that B sizes are halfway between A sizes. For example, a B5 notebook has more writing space than an A5 one, but is easier to carry than a full-sized A4 notebook.

However, the B series is a little more complicated because it’s different in Japan than the rest of the world.

A Semi B5 notebook is slightly shorter and narrower than a B5 (JIS) notebook. According to the Japanese Industrial Standards Committee (JIS), Japanese B sizes are a little larger than ISO B sizes. Because of this, B size paper from a Japanese brand is often, but not always, slightly larger than B size paper from a non-Japanese brand.

One exception to the trend is the B5 size. Some Japanese brands use a paper size that’s sometimes called Semi B5. At 7 x 9.9 inches, it’s similar to ISO B5.

Check the “Specifications” tab on a product page to see measurements. One very important thing to remember: while paper sizes are defined by international standards, that doesn’t mean every notebook from every brand is the same size. For example, an A5 Midori MD Notebook is 5.8 x 8.3 inches, while an A5 Rhodia Webnotebook is 5.6 x 8.3 inches.

At JetPens, we carefully measure all of the products shown on our website. If you need a specific size of notebook, be sure to check the “Specifications” tab on the product page.