German office paper follows a standard set in 1922. Walter Porstmann proposed it, and the standards committee founded in 1917 adopted it. Size A0 is exactly one square meter. The sides stand in the ratio of 1 to the square root of 2. Every smaller size comes from halving the one before, so a sheet of A4 is one sixteenth of a square meter. In everyday German, DIN A4 simply means an ordinary sheet of paper. The German standard later became the basis of the international standard ISO 216.