For example, A4 (297 x 210 mm) is the most common size of paper, and A5, which is half the size of A4, is the second most common size.
Have you made any sense so far? This system can also work backward. For example, to make an A5 sheet, we would just cut the longest edge in half, which would be 297mm in this case. So, 297/2 = 148, and an A5 sheet is exactly half the size of an A4 sheet, measuring 148 mm by 210 mm. In the end, it’s not that hard. But instead of figuring it out each time, you can always look at the table at the top of this page.
No matter how many times you double the short edge or cut the long edge in half, the width-to-height ratio of A-sized paper stays the same. A4 paper, for example, is 210 mm wide and 297 mm tall. Half an A4 is an A5, and two A4s are an A3.
A4 and A5 are the most common sizes of paper in the world. If you fold an A4 sheet in half along the shorter side, you can make A5 paper (148 mm x 210 mm, or 5.83 8.27 inches). A5 is also not good enough because it is too small for handwritten letters. A4 is too big and wastes a lot of paper. Even though A4 is the standard letter size, A5 is used for tabloids. Folding an A4 sheet of paper makes it an A5, which fits perfectly in a C5 envelope.
Have you ever looked at the computer paper you buy in great detail? Or are you good at letterhead and academic paper by nature? You may have heard of A5 and Tabloid, but for many people, the only page sizes that really matter are A4 and Letter. But there are a few sizes of paper that people use every day, and if you know what they are, you can print and copy documents faster and for less money.
Paper sizes are a subject that people talk about less and less in this digital age. When you do, it’s important to know how different sizes are different. How are A4 and A5 paper sizes different, and how do they compare to “letter size” paper in the US? What’s the difference between letter and A4? Anyone can understand anything better if they look at the history of standardization and the importance of international standards.