When your barber or hairstylist asks you for a number, what does it really mean? By now, it must be known that these are in a way related to the length of the hair. What haircut numbers actually are the fraction of hair that is to be left on the scalp.
For instance, if you've chosen say, number 2 it also means that 2/8 of your hair (if 8 were the maximum length of the hair that is allowed by the clipper used) will be left on the scalp. Generally, 8 is the highest haircut number while there can also be bigger clippers based on the length of the hair.