If you parted your hair into 1”x1” sections then counted the number of hairs in each section this would be the density. In general, most people will have thin hair around the temples meaning this area will have fewer hairs. The scalp is easily visible in thin sections without parting because the area is less dense. You will also find that most people will have thick hair in the back meaning this area will have more hairs. The scalp is not visible in thick sections without parting because the area is more dense.
Why is it important to know your hair density? It aids in styling. If your hair is thin, you should part in larger sections to show less scalp and make the hair appear thicker. If your hair is thick, you should part in smaller sections to define better and decrease some of the volume. Thicker hair will require more product than thin hair as there are more hairs to apply it to.
Your hair texture and hair density are independent of one another. Course hair texture and thick hair density result in the appearance of “bigger” hair. Fine hair texture and thin hair density result in the appearance of lesser hair. Texture is an important factor to consider in chemical or heat styling, while density is not.
My daughter and I have “big” hair but it is not the same. I have a thick hair texture and normal hair density. She has medium hair texture and thick hair density. If you saw our hair in a ponytail it would appear similar. However upon closer inspection you would find that she has more hairs per square inch than I do, while my individual hair strands are thicker.
So why is density important? It helps in determining how long a style will take and how much of a product will need to be used. Those with very thick dense hair may not want to take on pixie braids or mini-twists as these tiny styles will take longer because they have more hair. Also those with thin hair need not use as many rollers when curling their hair as they have less hair.