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How many hairs can you transplant into a square centimeter? I have a scar, and I want to fill it in. I am trying to find a doctor who can fill it in with just one surgery. Is this a reasonable question?

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An excellent question! The calculation is one that is used in the industry as a benchmark measurement. The average person with 100,000 hairs on his head has 1250 hairs per square inch or 193 hairs per square centimeter.

But what is the number to use in determining the correct density for a hair transplant? Some doctors use high density numbers to define how good they are. However, there is a balancing act between maximizing density at the time of a transplant surgery and maximizing growth months later. Experienced doctors are the key.

The reasonable upper limit of density numbers from a transplant perspective is up to 120 hairs per square cm. This type of density, however, requires supple skin that still has elastic properties. Scars do not have this characteristic. Also scars have an abnormal blood supply when compared with normal skin. Much of the infrastructure and microcirculation in the vasculature is not present in scar, so transplanting very high densities may not produce good growth.

You need to be examined by a hair transplant expert, who has the experience to give you a reasonable answer to your specific need. While I understand that you would like to have this completed in one surgery, that may not be in your best interest. Only your doctor will be able to advise you.


Hi, I am interested in possibly obtaining your services. In particular, I am interested in the FOX procedure. My problem areas are in the temple region. I live in MD so I have included some attatchments of the temple region. The ones that look like I have less hair is what I kind of look like in the morning. The ones that look like I have more hair is after I have brushed my hair. As my hair grows longer the hair around the temple region doesnt look as thick as the rest of my hair. I am currently taking propecia which seems to have stop the hair loss but I believe I started it a little to late to help my temple region. So my primary go is to thicken the areas of the temporal region. I may also be interested in some small things such as thickening some of my facial hair. If more pictures are needed I would be happy to get them to you. I am not sure what the next step is so I’ll be looking forward to hearing back from you. Thanks.

P.S. I am 27 years old.

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Nice to talk to you today. You reported that you have been on Propecia for 9 months. In addition, you saw a doctor from another clinic who suggested that you visit me and get an FUE (FOX) procedure into the temples.

I have reviewed your pictures. At 27 years old, I am generally very cautious. Before I would even consider adding hair density to the temple region, I would want to assess your overall future balding possibilities, looking for miniaturization throughout the head. I would also want to see what your temple densities are. As you are on the East Coast, I would recommend that you visit Dr. Robert Bernstein in New York where he can make such an assessment. He is an excellent doctor whose opinion should have great value. No one wants you to take unnecessary risks, particularly me, so a good opinion from Dr. Bernstein will determine the best approach. His website is


I looked over your site and noticed a wide variation in the amount of fullness with the same number of grafts between patients. For example, Patient BN has almost 2100 grafts and has a thin look, while Patient DP has 2500 grafts and had a full head of hair. If I go for a hair transplant, can I buy the fuller rather than the thinner look? I’d be willing to pay more.

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For reference, these are the two patients you mentioned:

I looked at the subjects you were talking about. There are many differences between the two patient’s hair characteristics that could explain the difference in the results. The finer hair of Patient BN is only 1/3rd of the thickness of the hair that Patient DP has. The distribution of the grafts and the number of grafts placed per square inch of balding area is different. DP has a stronger hair character than BN and the size of the balding area is much greater for BN, despite what these photographs show.

People with finer hair have lived their entire life with a thinner ‘see through’ look, in contrast to the ‘gorilla’ look of the coarser haired person. Your results will reflect the ‘building’ materials your hair has in your donor area (like a 2×2 as compared to a 4×4 piece of wood). The key here is to give you a look like you had before you started to bald.

To answer your question, the fees are based on the number of grafts, not your hair characteristics.


Dear Dr. Rassman,
Thanks for taking the time the other day to visit with me and also for the very informative follow-up letter and your recommended plan for my hair transplantation. Over the last two months I have been seriously looking into the hair restoration field and have read three credible books and studied every web site of every accredited hair doctor. I also consulted with doctors that I felt were very respected in hair restoration. My conclusion is that I need to stay on Propecia consistently to preserve the hair I have right now and use the follicular unit transplantation (FUT) technique exclusively, to replace the lost hair.

But I am confused by the number of grafts recommended. So far, I have heard various numbers ranging from 1,000 to 3,000. After visiting with you and hearing your recommendation of 2500 grafts, I wrote back to a very reputable doctor who had recommended a session of 1,500 grafts and told him that another clinic had recommended 2,500 grafts. He then told me that 1) each person has very limited donor supply and one must plan a session based on future hair loss, and 2) the survival rate of transplanted grafts deteriorates as the number of them placed close to each other is increased, as is done in megasessions. He told me that other clinics have no guarantee or refund policy if the hair follicles don’t grow back, so they just transplant as many as possible, even if not safe for the patient.

So my questions are:

  1. What does ‘limited donor supply’ mean in my case? You saw my hair, how many good donor grafts in total do you think I have for now and the future? What would it be if Propecia did not work and I continued to lose hair?
  2. Have you seen any side effects with larger sessions such as more noticeable scar in the donor area, loss of transplanted grafts, excessive swelling of the forehead or longer recovery periods?
  3. Do you or can you guarantee a certain survival rate for the transplanted grafts?

I appreciate the time you have taken to help me with my hair loss problem. I guess I can’t help it, I am a natural engineer, and this being the most important decision I probably ever make I have just been researching the hell out of it! I am confident, however, that I am talking to the best source there is out there.

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Part of what is important about being a doctor is the concept of mutual respect. The person who wrote the email to me on this blog, is analytical and clearly fully aware of the subject material. Good communication produces respect so a doctor should spend an appropriate amount of time and focused attention to address your concerns at the interview and in followup to that interview. I would welcome a call from you to elaborate on this blog answer.

  1. Some people do not have the donor supply and when that will be an issue, I tell them. The amount of donor hair is a calculation of density in the donor area plus laxity of the skin. Finally, the size of the bald area and the final worst case pattern must be taken into account. As measurement is critical to this process, one must make direct measurements of the density in the donor area. I was the first to publish on the measurement of the donor supply and the instrument I invented to do this is now used by every competent doctor in this industry. There are no other instruments that are used for hair measurements that do not fall under my U.S. Patent. The average patient has about 6,000-12,000 grafts to move but the wide spread reflects the many variables discussed above.
  2. If you come to our free open house events, you will meet people who had thousands of grafts and see for yourself what happens. The key to understand the safety of large sessions is to meet directly with many people who had them. I would not be doing large sessions if they were not as good or better than multiple smaller sessions. With good decision making by the doctor, large sessions should not scar more than multiple smaller sessions but there may be a cost for aggressive decisions in large session transplantation if the doctor is not experienced in such procedures.
  3. This type of complaint usually reflects the act of denial which most people exercise when they forget what they looked like ‘before’ the started the hair restoration process. Sometimes, people continue to loose hair and think that the new hair loss reflects a transplant failure when it really reflects the unpleasant idea that balding continues. To address the growth of the transplanted hair, wWe guarantee our work. Anything that does not grow, we will replace at no charge. This almost never happens, so I rarely discuss it unless asked.


I am a 26 year old male, who has had two hair transplants in my frontal area. The density of hair in my transplanted regions is much lower than that of my natural hair, and hence looks a bit unsightly. I want to know if there is a limit to the number of FU grafts one can transplant in order to improve density. If so, what are the dangers of exceeding this limit?

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The normal hair densities of non-transplanted hair are measured at 193 hairs per cm squared (97 follicular units per cm square). A transplant doctor can put in densities of half of that in a single session. If you have thinning hair, then your density is not up to a level adequate to appear full. There are no inherent dangers in dense packing the hair in a transplant surgery provided that the doctor’s team is able to do it.

Dense packing, a technique we defined in 1993, makes for less surgeries and more fullness. If the wounds are over a particular size (more than 1.7mm each) then the risks start impacting the patient, for example, with regard to blood supply. If the wounds are smaller than 1.7mm, then the risks of dense packing of the grafts all but go away. We use wound sizes of about 1mm (the size of the wounds vary with each patient). The smaller the wounds, the faster the healing. Healing in this context means that the wounds on the skin become almost impossible to see, something that usually takes a day or two on most of our patients. Wounds greater than 1.7 mm, tend to show for longer periods. Some transplant patients in the old days saw wounds measuring 3-4 mm each (the old plugs), and they were visible for weeks after the surgery.


How many micrografts are there per cm2?

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The density on the human scalp is 193.75 hairs per square cm or 1250 hairs per square inch. The average human head has 80 square inches to it which translates to 100,000 hairs on a typical Caucasian. Asians have about 80,000 hairs and Africans have about 60,000 hairs. Assuming the average follicular unit has 2 hairs each (typical Caucasian), that would put the numbers at 100 follicular units per square cm in a typical non-balding Caucasian. Doctors can transplant (with modern dense packing techniques) about 50 follicular units per square cm (100 hairs on average) when indicated. Clearly there issues that logically should point to how much coverage can one get. The higher the density, the smaller the area of coverage (assuming supply limitations which are always a factor) In a very bald person, it would be virtually impossible to transplant such high densities to cover the entire balding area as the supply would clearly not meet the needs. So the artistry of the doctor becomes important to maximize the characteristics of the patient’s hair.


I am a 23 year old male with an extensive family history of balding. I am well on the way to follow my father and grandfather’s pattern. What can I do?

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I just had a patient of the same age and with the same problem in my office, so I thought it might be worthwhile to read what I wrote to him. I send comprehensive letters like this to all of my prospective patients out of respect. It is always an honor to be able to play such an important role in the life of a patient.

Here’s the letter:

You have an unusual problem found in less than 1% of balding men. Your donor hair density in the rim of ‘permanent’ hair around the side and back of your head is higher than average (300 hairs/cm2 while the average is 200 hairs/cm2) but 1/3rd of these hair show miniaturization. This is the same process that goes on in the balding area on the top of your head and it should not occur on the side and back. When it does, it reflects a condition we have defined in the medical literature which we call Diffuse Unpatterned Alopecia. In essence, you have a process going on throughout the hair on your head, even the ‘permanent’ zone. Now with that said, your effective donor density of 200 hairs/cm2 (which reflect the sum of your hair count less the miniaturized hairs) is from a practical point of view, normal. But the fact that you have this process going on in the permanent zone means that the future of your permanent hair is uncertain. In my fairly wide experience, people who have had Diffuse Unpatterned Alopecia, have not experienced progressive extensive balding in the ‘permanent’ zone, but there is not certainty in your future. In determining your predicament, I would like to call your attention to some of the other elements of the examination I performed on you. Your hair is more coarse than most people, which means that the value of each hair is much higher than a normal person. There is a slight wave to your hair which means that it grooms and covers well with its strong character. Your hair is black and your olive colored skin provides moderate contrast between your hair and skin color, and although your olive skin offsets the dark hair a bit, it still calls attention to a lighter background which might require more coverage to get a full look.

Your biggest problem is the extent of your balding, which appears well on the way to becoming a Class 7 balding pattern (the most advanced pattern) and one that runs in your family. At the age of 23, you have a typical early appearance of this advanced balding process, but that balding process although mild in the top and crown of your head at this time, may respond well to the drug Propecia. You indicated your objection to using this medication to slow down or arrest the hair loss in the top and crown area. Your objections are over the side effects of the drug (rare and unusual). Considering your age, you have a good chance to get some reversal of the balding process in the top and crown area. With the diagnosis of Diffuse Unpatterned Alopecia that we found our your examination, I see even more reason to use the drug. I have seen fully half of the men who take Propecia see some reversal of the diffuse hair loss process in the ‘permanent’ zone, giving you two reasons to reconsider your position against taking this drug.

When dealing with a young man, I tend to be conservative, leaning on the drug treatment to slow down the balding process and for the maturity of the patient to line up with the extent of the problem. By saying this, I do not mean to be offensive, but young men are driven for now answers and often do not see themselves through the entire balding process which may take years. Transplantation, although a wonderful solution when appropriate, is the wrong answer for those who have not worked out a Master Plan with a good doctor that accounts for the worst case scenario of the balding process as modified by a transplant program. That is the dilemma before you and I at this time. You have to convince me that you understand what I know about your hair loss and what can be and can not be done about it. I must understand your maturity in dealing with a transplant program that will be with you the rest of your life. A good doctor/patient relationship is what I am talking about, something that is not easy to obtain in an hour visit to my office.

I am not firm against a transplant solution for your balding but because of the Diffuse Unpatterned element of your Alopecia, I need some comfort that whatever we plan is going to be the right plan for you. I want to speak with you again about the Propecia option and dive more into depth on the various subjects we discussed. We spent a great deal of time discussing the safety issues with Propecia, hopefully giving you more comfort in considering this drug as part of the long term treatment of your progressive hair loss problem.


Thanks to everyone for the great emails. Keep them coming in! Here’s one I received on Tuesday, but didn’t get a chance to answer until today…

Dear Dr. Rassman,
I have a slightly below average donor density and I am wondering if a hair transplant would be sutable for me. I am 33 years old and last year started receding agressively. I think I am NW 5 heading to 6. How many graft can you take from my donor for me to have a full coverage? In other words: How many total grafts does my donor have?
Thank you for your attention.

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There are five characteristics that vary with each person, that determine the value of the hair for a hair restoration procedure. They are:

  • Density of the hair. Yours is lower than average, but that in itself does not necessarily mean that you are not a good candidate
  • Hair shaft thickness. The coarser the hair, the better it supplies bulk. Hair bulk is a critical element in producing fullness and coverage.
  • The size of the balding area. The more bald you are, the more hair you might need. Sometimes, the goals may be changes to adjust to limited supply or a demand that is too high. That is something you must work through with your doctor.
  • The characteristics of your hair. African hair is the best because it wants to cover, good wavy hair is the next best because it wants to flow together. The Italians and French had the best wavy hair. Straight is the most challenging, as found in many Asians.
  • Color/contrast between hair and skin color. This is critically important. A Class 6 pattern blonde person could reduce his hair population to 85% of its original density and still look full as the blonde hair and blonde skin have low contrast. The same applies to black hair and black skin, brown hair and brown hair, sandy hair and sandy skin and any skin color with white hair. Salt and pepper hair works very well and I have produced some amazing results in very bald men with very little hair.

The amount of hair needed to transplant depends upon many things. Look at our website and see the hundreds of patients there, many who show balding patterns similar to your. The number of grafts are clearly defined for you to see.


What is the limit for transplant densities?

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Hair can be transplanted at a density that approaches 35% of the original density in many people. The ability to place such densities depends upon many factors which include: hair thickness, skin characteristics, the size of the instruments for making sites, the skill of the surgical team at placing grafts tightly together and the processes that reflect the quality management of the surgical team. Not all doctors can place, for example, two hair grafts into a 0.9mm recipient site. Even in the hands of a good surgical team, not all hair grafts can be placed into a 0.9mm recipient site. So there is a balance between what can be done and what should be done. A surgeon with considerable experience in hair transplantation dense packing is best able to make the judgments required for maximizing hair densities. I pioneered Dense Packing with the first published mention in a 1993 article in the Hair Transplant Forum and have been using this technique ever since. More recently, we have moved to combining Dense Packing and Large Session surgeries to maximize yield and reduce the number of surgeries required to get a person to his goal faster.


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