Its a tricky question.
If someone has very small bald area, say 10 sq cms, he/she can expect very high density. But its very rare.
Graft requirement will always be more than your donor availability. A bald person always wants / needs more grafts than his donor capacity. Imagine if you are completely bald by 100 sq cms, you would need 50 grafts per sq cm to have complete density. i.e about 50,000 grafts. No individual will have 50,000 grafts donor. If we harvest all 50,000 grafts from donor, back side of head will become complete bald. We have to extract grafts in such a way that back side of head looks normal (baldness not noticible) and also covers the frontal / top bald areas with aesthetically improved change in appearance.
One can undergo hair transplant to the max limit of his donor capacity. Donor can be either from back side of scalp or beard or chest or from any other body parts.
One graft at PIONEER equals about two single follicles of hairs i.e two hair strands. To know graft count which can bring aesthetic change in your appearance please click here.