How many hair grafts I need to cover the bald areas on my head? (Photos)

Looking at your donor area i can say that you can get 3000-3500 grafts. İf you want higher number, your beard can be used as the donor area as well.

You can estimate your hair transplant graft count by by looking at the Norwood scale to see where you fit it. Take the number of your hair loss stage and multiply it by 1000-1500. As many of doctors have estimated a minimum of around 3000 grafts, you can see a general example of the type of coverage possible on the patient below from the Dr.U Hair Clinic in Los Angeles. In this case, a strategic, diffuse placement was able to achieve a significant improvement. However, the actual coverage possible can differ depending on hair thickness and waviness as well as hair to skin color contrast. At the bottom of the article, you will find a gray tab for our hair transplant graft calculator which you can also use. 

Photos cannot determine if you would be a good candidate for surgery.  You need an examination and the doctor needs to understand your goals and expectations.
You need to have good communication with your doctor to understand what your end result will look like. 
Someone with your hair loss pattern may be perfectly happy with 3000 grafts, while others (with your same hair loss pattern) may not be happy even with over 6000 grafts.  Finally if you keep your hair as short as you do on the photos you will not likely be happy with the results since hair transplants cannot give you back the density you once had.

The number of grafts needed will  be determined by what a patients goals may be. Hairline restoration vs. adding density to a thinning crown will necessitate different counts. Addressing both will often times require multiple procedures. 
A good rule of thumb is that 1200-1500 grafts will be needed to restore a receding hairline. 2000 grafts will add reasonable density to an area of the crown about the size of a compact disc. 
Based upon your photos alone, I would venture to guess that you may need ultimately need upwards of 3000+ grafts (split between 2 procedures), if the goal is to restore good density throughout. You may want to consider strip grafting vs. FUE. While FUE will allow you to avoid a linear scar there is a limit to the amount of grafts which can be harvested (10-15%) before one begins to experience thinning at the donor site. This is not a concern in strip grafting where the donor site is excised and all of the follicles in a given area can be harvested (simply put...no bald spot).
As always, discuss your concerns with a board certified plastic surgeon (ABPS) with experience in hair restoration.

Although it is always preferable to consult with a surgeon to asses fully and realistically what can be achieved it seems like you would need to undergo 2 hair transplants in order to cover your balding / thinning areas. 3500-4000 grafts is what would be needed and that would be achieved over 2 sessions with a year break in between both. The reason why 2 sessions is needed is because of how much is permitted to extract from your donor area based on its' density and quality. You never want to over harvest the donor area or you will end up looking like hair is missing.

hello,you need a consult to discuss more than how many and what your goals are.  Looking at your pattern, you will need several full sessions.  2000 grafts per session to address your balding fully.Dr. Peter Malouf

You should meet with a good doctor to determine (1) if you are a candidate for a hair transplant and (2) based upon the examination of hair type, thickness, prediction of your future balding pattern and donor density, what is in your best interest. People with low donor densities are often not great candidates for hair transplants because the demand for hair exceeds the supply availability. Depending upon the thickness of your hair, it could take anywhere between 3000-4000 grafts if you have the density to support it.