What is the size of A4 paper?
The size of A4 paper in cm is: 21 x 29.7
The size of A4 paper in mm is: 210 x 297
The length of the diagonal is 363mm or 36.3 cm but usually we don’t use this dimension for papers as we do for TV screens or computer monitors.
A4 is the standard dimension of paper used in the printers and copiers (copy machines) all over the world. It is the dimension you usually shop in rearms of 500 sheets. We measure the quality of paper in GSM (grams per square meter). The standard weight of the paper we use in printers is 90-100GSM. Thinner papers (bellow 75GSM) are not suitable for general use. Thicker papers (110-150 GSM) is suitable for brochures and posters. 200+ GSM is like magazine covers.
To see the dimensions in inches click here
Learn more about the paper size system in wikipedia