Is there such thing as normal scalp hair density?

The key to being human is that we're all different. The same is true for hair density. In fact, there's really no such thing as normal density. Men and women have have different hair densities.  Caucasian individuals have different density than those of African/ Afro-carribean background, and different than those of Asian background.

Normal hair density if one was forced to quote a normal value is somewhere   between 165-220 hairs per sq cm ( ... or roughly 87 follicular units to 120- follicular units per sq cm). The back of the scalp is thicker than the temples.  he highest density occurs at birth (when the head is very small) and then slow reduces as the individual gets older.