A3 refers to a paper size that measures 11.7 x 16.5 inches or 297 x 420 millimeters. It is part of the ISO 216 standard, which defines various paper sizes used internationally. A3 is commonly used for printing large documents, posters, and diagrams, providing more space for detailed information compared to standard letter-sized paper. In addition to its use in printing, A3 paper is often utilized in professional settings for presentations and design work. It is popular among architects and graphic designers for creating layouts and visual materials. The larger format allows for better visibility and clarity in displaying complex information.