A4 (16k) 297mm×210mm;
A5 (32k) 210mm×148mm;
A6 (64k) 144mm×105mm;
A3 (8k) 420mm×297mm;
Note: A3 (8k) size has not been fixed yet, but it is commonly used.
A4 copy paper in daily life, 8K paper refers to these sizes, that is, the size of A4 paper (16K paper) is: 297mm×210mm, and the size of 32K notebook (A5 notebook) is 21cm × 14.8cm.