There are two different ways to estimate the amount of hair needed. The golden standard by most doctors is per number of grafts or number of follicular units. The second way that some doctors use is the number of hairs transplanted, In each graft, there may be one, two or three hairs, and depending on the number of hair in each graft, they are used appropriately in the recipient area. However, it is also good to know how many hairs were transplaned. This way you can have an idea of the overall look after the hair grows in, keep in mind that 2000 grafts at one clinic may give a very different result at another clinic depending on what proportion of one, two, or three hair grafts was used. For example if 2000 grafts were all one hair units the total number of hairs would yield 2000 hairs. But let say with 2000 grafts, there was 500 ones, 500 twos and 1000 three hair units, in this case the total hair would be 4500 hairs. So it is important to know both the number of grafts and also the total number of hairs that was transplanted.