A4 size is a standard paper dimension commonly used in many countries around the world. It measures 210 millimeters in width and 297 millimeters in height, which is approximately 8.27 inches by 11.69 inches. This size is part of the ISO 216 standard, which defines various paper sizes based on the metric system. A4 paper is widely used for printing documents, letters, and reports. It is popular in offices, schools, and homes due to its versatility and compatibility with most printers. Many notebooks and stationery items are also designed in A4 size, making it a convenient choice for everyday use.