During your lifetime, the average human will grow 591 miles of hair. Unverified But hair does grows about 6 inches per year and the average head has 100,000 hairs. Take an average lifespan of 67.2 years. 6 x 100,000 x 67.2 = 40,320,000 inches = 636 miles. Unfortunately hair growth is not uniform through out your lifespan, I have yet to find a formula for this, but this would be pretty close.