what is the ratio of a4 size paper

The ratio of A4 size paper is approximately the square root of 2 (1.414) to one. This means that the long side of the paper is 1.414 times the length of the short side. The dimensions of A4 paper are 210 mm x 297 mm, or 8.27 inches x 11.69 inches. The aspect ratio of A4 paper is the same as all other A series paper sizes, which is 1:1.41421.