The number of grafts required to treat an area depends on a number of factors, hair characteristics and the size of the surface area to cover.
Hair is placed into the recipient area in natural bunches of hair, follicular units, also known as grafts. The scalp can be approximately divided in to the 3 main areas, hair line and frontal third, mid-section and crown. The hair line needs to be made of single hair follicular units, 1 hair grafts; the number of single hair units will differ dependent on the density needed to be placed and the hair line design, can range from around 400-900 FU´s.
Behind the immediate hair line 2,3 and 4 hair units are placed in the frontal third, and dependent on the hair line design can require from around 2500-3500 grafts, including the hair line grafts. The mid-section is the area between the frontal third and the crown, the surface area will vary dependent on factors such as how broad the head is and whether the lateral humps are showing signs of miniaturisation.
This can add an additional 2000 plus grafts to the frontal third total, anywhere between 4500 to 5500 plus grafts in total. The crown or vertex can have an insatiable appetite for hair as it can open on both sides and drop down the back of the scalp, from a classic NW5 to NW7.
If the crown expands aggressively the surface area can reach the same as the frontal and mid combined, making total restoration impossible in some cases and in others a reduced density may have to be placed. It is common even with a smaller crown that a lower density needs to be placed to give total coverage. The graft count for the crown can vary greatly, from 1500 to maybe 3000 grafts, assuming the donor hair resources allows. Total restoration can require around 7-10,000 grafts, it is not always possibly to safely extract this from all candidates. It is important that prior to your first surgery a long term plan is made and take into consideration aspects such as age, donor supply and progressive hair loss.