D1 size (532 × 760mm | 20.9 × 29.9in) from Chinese Paper Sizes

The Chinese standard GB/T 148-1997, which replaced GB 148-1989, documents the standard ISO series, A and B, but adds a custom D series. This Chinese format originates from the Republic of China (1912–49). The D series is not identical to the Swedish D series. It does not strictly follow the same principles as ISO paper sizes: The aspect ratio is only very roughly √2. The short side of a size is always 4 mm longer than the long side of the next smaller size. The long side of a size is always exactly – i.e. without further rounding – twice as long as the short side of the next smaller size.