How much of the implant size is lost when it is place under the muscle?

It is believed that you lose about 50cc when the implant is placed behind the muscle.   I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS), a member of the American Society of Aesthetic Plastic Surgery (ASAPS), and a fellow of the American College of Surgeons (FACS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified, Double Fellowship-Trained Beverly Hills Plastic Surgeon

I think the implants may look a little smaller when they are "squished" under the muscle and after the swelling has decreased but they don't actually lose volume. We tend to tell pts to chose a slightly larger to be close to their final goals for breast augmentation. Make sure to see someone with board certification in Plastic Surgery.

Thank you for your questions. I do not think that any of the implant size is "lost" under the muscle. I think that early after surgery there is swelling and elevation of the implant when placed under the muscle and this leads to a larger than expected outcome initially. When things settle and heal, the size and fullness appears to decrease and patients conclude that some volume is "lost." I would say you need to go through a consultation with a board certified plastic surgeon and let him or her guide you through the process. If in the end you are between 300 and 325 cc, and you are worried about being too small, choose the larger implant. If you are an A cup now, an implant in the 300 cc range should provide you with around a 2 cup size change in the end.Hope this helps!

Dear mkla,Breast implant type and sizing selection is a complicated process and requires a detailed consultation that includes a discussion of your goals, a detailed examination, and a lengthy discussion. But the decision will always start and end with the patient. When it comes to sizing, we have all of our patients find 3 photos of their desired breast size. We ask for naked breast photos because clothing can obscure the true size (push up bras). Next, we consult with patients and go over the photos and take detailed breast measurements during a physical exam. Next, we using a sizing algorithm to determine a range of implants that will work based on the exam and the measurements.Lastly, during the operation, we use silicone sizers in the operating room to see how the size actually looks in the breast. We sit the patient up in the operating room, while asleep of course, and compare the sizer result with their desired look photos. If it is too small, we start the process over with a slightly larger implant. We don't stop until we get the perfect match.Of all of my breast augmentation patients, every one of them has been happy with their size due to this detailed and meticulous process. You don't want to invest time and money into a result that is either too big or too small.You should discuss your concerns with a board-certified plastic surgeon and make sure that your surgeon understands your goals.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

is done with external sizers to help you visualize what outcome you will have.  Whatever sizer size you like, I always add 10% to the volume to achieve that look above or below the muscle.  If you don't upsize the implant, you will be smaller than what you were hoping for.  And if you limited your look to a C cup, best to bring in a bra you want to fill and use sizers to fill it, then add 10% that number for your implant size.  This is not 100% but has been very accurate over the course of my 25 year career.

Thank you for the question. In my opinion, it is not possible to accurately determine how many ccs (if any) a patient would “lose” when undergoing sub muscular breast augmentation surgery. I suggest patients do not make decisions based on statement such as: “you will lose 25 or 50 cc of volume when breast implants are placed under the muscle”. These statements are simply not reliable enough to utilize clinically. 
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery (regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work. Sometimes, it is necessary to seek several consultations before you feel comfortable about your choice.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "generous cup” etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size. The use of computer imaging may be very helpful during the communication process. The use of in bra sizers may also be helpful. In other words, use as many “visual aids” as possible during the communication process. I encourage patients to meet with me as my times as necessary, to feel comfortable that we are both on the “same page”.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery. I generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this helps. Best wishes.

You are missing the most important thing here. That is to choose the correct implant PROFILE to create the look you mean by a "generous C" result. Then get that implant in the right diameter for your chest width. The volume is just what it takes to fill up that implant.