How do you compare different paper sizes? Aside from the standard A4 and B5, what are the C series, Kikuban, and Shirokuban? If you find yourself puzzled by the various paper sizes when you want to print documents, produce products, or customize books, don’t worry. This article will explain the sizes of different paper standards and provide a comparison table for easy reference, helping you understand at a glance!
To understand paper sizes, you first need to know what standards exist. Generally, paper specifications can be divided into two main categories:
The International Organization for Standardization defines it as including A series (A0, A1, A2, A3, etc.), B series (B0, B1, B2, B3, etc.), and C series (C0, C1, C2, C3, etc.). The sizing method is easy to remember: each size is half the size of the previous one. For example, A1 is half the size of A0, A2 is half of A1, and so on.
In Taiwan, when you buy paper at a store, you often see sizes marked as “1K,” “2K,” etc. These specifications apply to Kikuban (GK) and Shirokuban formats, both of which have been used since the Japanese colonial period. The Kikuban size is closer to the ISO A series, while the Shirokuban size aligns more closely with the ISO B series.
💡 Reminder: Manufacturers may slightly adjust the sizes of Kikuban (GK) and Shirokuban formats to align with ISO international standards or printed product dimensions. Therefore, the dimensions from different manufacturers might vary slightly, so it’s essential to pay extra attention when comparing sizes.
After understanding the classification of paper sizes, let’s examine the detailed size comparison chart.
| Spec | A Series（mm） | B Series（mm） | C Series（mm） |
| Size Illustration Diagram |  |
 |
 |
| 0 | 841 x 1189 | 1000 x 1414 | 917 x 1297 |
| 1 | 594 x 841 | 707 x 1000 | 648 x 917 |
| 2 | 420 x 594 | 500 x 707 | 458 x 648 |
| 3 | 297 x 420 | 353 x 500 | 324 x 458 |
| 4 | 210 x 297 | 250 x 353 | 229 x 324 |
| 5 | 148 x 210 | 176 x 250 | 162 x 229 |
| 6 | 105 x 148 | 125 x 176 | 114 x 162 |
| 7 | 74 x 105 | 88 x 125 | 81 x 114 |
| 8 | 52 x 74 | 62 x 88 | 57 x 81 |
| 9 | 37 x 52 | 44 x 62 | 40 x 57 |
| 10 | 26 x 37 | 31 x 44 | 28 x 40 |
| Kikuban size | centimeters | Shirokuban size | centimeters |
| G1K | 63.5 x 88.9 | 1K | 78.7 x 109.2 |
| G2K | 44.45 x 63.5 | 2K | 54.6 x 78.7 |
| G4K | 31.75 x 44.45 | 4K | 39.4 x 54.6 |
| G8K | 22.23 x 31.75 | 8K | 27.3 x 39.4 |
| G16K | 15.88 x 22.23 | 16K | 19.69 x 27.3 |
| G32K | 11.18 x 15.88 | 32K | 13.67 x 19.69 |
| G64K | 7.95 x 11.18 | 64K | 9.86 x 13.67 |
| G128K | 5.59 x 7.95 | 128K | 6.83 x 9.98 |
With so many paper-size specifications, can they be converted? As mentioned, Kikuban is closer to the ISO A series, while Shirokuban aligns more with the ISO B series. Thus, if you want to compare standard sizes, the table below may help:
| Standard Sizes | Corresponds to Kikuban | Corresponds to Shirokuban |
| A4 | G8K | 10K |
| A5 | G16K | 25K |
| A6 | G36K | 49K |
| B4 | G4K | 8K |
| B5 | G8K | 16K |
| B6 | G25K | 36K |
21 cm x 29.7 cm, the most commonly used paper size internationally.
17.6 cm x 25.0 cm, commonly called 16K size in Taiwan for custom notebooks.
14.8 cm x 21.0 cm, commonly referred to as 25K size in Taiwan for custom notebooks.
Where are the different sizes of paper commonly used? What size books do we usually read? Let’s explore the typical applications of various paper sizes:
Generally, the A series sizes, such as A4 and A5, are most commonly used for printing documents. These dimensions are also frequently used for producing books, manuals, and magazines.
A4 is one of daily life’s most standard paper sizes, measuring approximately 21 x 29.7 centimeters. This paper is widely used for printing, copying, and document filing. Its moderate size makes it easy to carry while accommodating enough content, making it suitable for various office and academic purposes. Whether writing reports, designing presentations, or creating posters, A4-sized paper is an ideal choice.
The B series is commonly used for posters, art papers, or commercial advertisements. Additionally, B5 is also a popular size for printing purposes.
The C series is mainly used for making envelopes and can correspond to the A series paper sizes. For example, if the letter paper is A4 size, a C4-size envelope can be chosen; if the letter paper is folded in half to A5 size, a C5-size envelope would be suitable.
Here is a detailed comparison and conversion chart for various paper sizes. Given the multitude of size specifications, it’s natural to have some questions, so we’ve compiled a couple of FAQs to help clarify any confusion:
Generally, ‘K’ refers to how many sheets can be cut from a full sheet of paper. For example, an A5 size (25K) means that 25 sheets can be made from a full sheet measuring 31″ x 43″. If converted to Kikuban size, only 16 sheets can be made from a full sheet measuring 25″ x 35″; hence, it is called G16K.
As each specification results in different full sheet sizes and there are also different standards like the US and Japanese regulations, discussing paper sizes with others can lead to misunderstandings due to the use of various standards. Therefore, when talking about with others or manufacturers, it is recommended to use centimeters to avoid confusion.
In the commonly used Taiwan Shiroku Ban, a full sheet is approximately 78.7 cm x 109.2 cm, 31″ x 43″.
For the commonly used Taiwan Kikuban, a full sheet is approximately 63.5 cm x 88.9 cm, 25″ x 35″.
Do you now have a better understanding of the various paper sizes? If you want to know which sizes are most commonly used for the planner you typically use, I recommend referring to Leatai‘s planner size guide. It will provide more detailed information about paper sizes and other related insights!
11 F., No. 168, Jiankang Rd., Zhonghe Dist., New Taipei City 235, Taiwan 
Tel：+886-2-8227-8800
Fax：+886-2-8227-9191