Genetics, lifestyle, and medications all influence the number of hairs on a head at any given time. Everyone has a different number, and this number lessens as we grow older. Hair density peaks at around age 16, and then begins to decrease over the course of one's life. Don't despair, though, you've got plenty of hair. The average human has 2,200 hairs per square inch, or 100,000 over the entire head.
Natural blondes tend to have the most hair, or the highest hair density. The average blonde has 140,000 individual hairs.
People with naturally red hair tend to have fewer individual strands than other hair colors. Most redheads have about 80,000 to 90,000 hairs on their scalps.
Darker hair falls between blondes and redheads, so most people with brunette or black hair have around 100,000 hairs. Darker hair is coarser than blonde hair, however, so it may appear more plentiful.
Hair texture is often confused with hair density, but they're not the same thing. Density refers to the actual number of hairs per square inch (so redheads have lower density than blondes). Texture refers to the actual thickness and shape of each individual strand. The texture of an individual's hair determines whether it is curly, wavy or straight. Density and texture work independently of each other, so it's possible to have low-density thick hair or high-density thin hair.
The average person loses about 50 to 100 hairs every day. Each individual hair only lives for three to seven years before falling out. This means that over the course of your lifetime, you'll have an entirely new head of hair over ten times.