While counting each single hair on the head is almost impossible, it is possible to average the total hair coverage. Have another person measure the edges of hair coverage on your head, and multiply to get an approximate area in square centimeters. Then, measure one square centimeter and have the other person carefully count the hair follicles in that area; use a magnifying glass and a bright light, and if it is hard to stay inside the cm^2 boundary, use a non-permanent marker to outline the boundary. Make sure the area selected has average hair growth, not a balding spot. Once you have a follicle count for that area, you can repeat the process until you feel you have enough for an average; five or ten counts should be enough. Divide the total number of hair follicles counted by the number of areas measured to get the average. Then, multiply that average by the total square centimeters of hair coverage on the scalp, and you'll have a reasonably approximate count of all the hairs on your head.