What would 450cc look like on me? I'm 5'7", 150lbs, and measured at 12.

It is very difficult to determine the exact size and shape implant you will require to best match your ideal breast image without an examination by a board certified plastic surgeon. Not just any board certified plastic surgeon, but one with many years of frequently performing breast augmentation surgery including different approaches, techniques and implant choices. This is because several measurements not to mention your breast characteristics are needed to determine the optimal implant size to obtain your goals. Without knowing these dimensions it would be difficult to make this determination. For example, the existing base width of your breast will determine, in many cases, the maximal volume per implant profile that you can accommodate. To illustrate; a 100 cc difference may make a significant difference with a narrow base width breast, but much less of a difference if you have a wide chest wall and wide breast “foot print”. Therefore, just because your friend may have a great result with let’s say a 350 cc implant to make her go from a “A” cup to a “C” cup size does not mean that you will have the same result with the same size implant. . Further simply placing implants in a bra to determine the size best for you is not always accurate as the bra often distorts the size, is dependent on the pressure the bra places plus the implant is outside your breast and not under it among other variables. Computer software morphing programs that automatically determine the best implant size can be helpful in some but not all cases (e.g. doesn’t work well in my experience with existing implants, sagging or asymmetric breasts). Using “want to be” photos however are useful if simply provided to the surgeon as I will further explain in the below link.

Congratulations on getting the process started!  In my practice I use three techniques to help patients settle on a size.  First is to ask patients to bring in goal photos.  In this way I am asking them to focus more on the "look" they are trying to achieve and to think less about cc's or cup sizes.  Second, as you have already tried, I use external sizers to allow the patient to see themselves with different volumes.  Third, I use 3D imaging which shows you different implant styles and shapes and the 3D rendering of your postoperative expectation.  Using these techniques I have found success in narrowing down a patient's desired implant size to within 25cc of a particular number.  Certainly discuss this with your surgeon and seek out several opinions until you feel comfortable moving forward.  Good luck!

You will not know until they are in your body and you look in the mirror.  You cannot accurately predict the exact result in advance.  There are many factors that influence the final result. Rib cage size and shape, muscle mass and location, breast tissue volume, shape, and elasticity, over muscle, under muscle, height, weight, body shape,  etc.  The same implant will look different in different patients. We tell our patients not to fixate on implant size.  We want to know what look the patient has in mind and then use sizers at surgery to determine the best size and shape implant for that particular patient in the operating room. The final result depends on what the patient has to work with.  The better shape the original breast, the better the final outcome.

Do a baggy test at home with the bra you want to fill. This will give a rough idea for you,. Best of luck.

Hello and congratulations. The 450s can provide a nice full breast depending upon your frame. Ask your surgeon about using a simulator to help you to visualize your results. 

The real question for you is what do you wish to look like. There is no reason to choose the 450cc when there is a very large array of implant choices, one of which will be just right for you.

Thank you for the question. Although useful as rough guidelines and as communication tools, all the modalities currently used to predict what breast implant size/profile will best achieve a patient's goals with breast augmentation are not very accurate, in my opinion. The use of sizers placed beneath a patient's bra, goal pictures, computer imaging technology… are all useful, but not necessarily as accurate as one would hope.
In my opinion, nothing will replace careful verbal preoperative communication with your plastic surgeon, preferably in front of a full-length mirror along with the use of as many "communication" tools” listed above.
In my practice, I use all of the above modalities and then use intraoperative temporary sizers to help determine the best breast implant size/profile to achieve a patient's specific goals as closely as possible. For this reason, I think it is helpful to have the entire range of breast implant sizes/profiles available in the operating room.
Achieving realistic expectations prior to proceeding to the operating room is also an important part of the preoperative communication process. Patients should be aware that the results of their breast augmentation will not necessarily match exactly what they are visualizing with anyone of the above-mentioned communication tools.
Given your questions and concerns, and given that your surgery is coming up soon, I would suggest that you schedule additional time to spend with your plastic surgeon. This additional time spent will be helpful in the communication process and in alleviating some of your anxiety.In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural” or "C 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, the use of computer imaging has been very helpful during the communication process, in our practice.Best wishes; hopefully you will be very pleased with the outcome of the planned procedure.

If you are breast base diameter was 12 cm a 450 cc moderate plus profile breast implant is too large for your breast.  You may be able to accommodate a 450 cc high profile implant by do need to discuss this with your plastic surgeon in detail.I agree with you trying the Rice bag test at home as another good way to estimate what size is best for you.  To learn more about breast implant sizing please read the link below:

The same size implant produces different results in different individuals. I prefer to utilize computer imaging to allow the patient to see what she will look like with different sizes and shapes of implants in and out of clothes. We also use a technology that allows you to look down at your body and see the result.

How to Pick the Right Size and Shape of Breast
Implants

One of the more frequent questions I'm asked as an aesthetic plastic
surgeon for patients considering breast implants is "how do I know what
size, and shape I need?” The answer
to this question has changed dramatically throughout the 25 years that I've
been doing breast augmentation. I've also learned that the words that patients
used to describe either what they want or don't want can be completely
misleading into what I interpret their meaning to be. Therefore, I like to
request that our patients considering breast augmentation bring in photos of
both what they think they like and what they don't like. There seems to be a
multitude of sources on the Internet where these photos can be downloaded. By
looking at the patient's desires, I get a better understanding of what they
want. We no longer recommend that we place the exact implant on top of the existing
breasts and then place a stretchy bra over it to give us any idea what that
exact same implant under the muscle would produce in size. That method, in my
opinion, will always over represent what the actual result will be. If you are
going to use a sizing type method, then Mentor makes a shell sizing system such
that, when the shell size corresponding to the implant that it represents is
placed over the existing breast and in a bra, it will better represent what
that size implant under the breast and muscle will look like. We've also used
3-D imaging called Vectra® since its inception some 6 to 7 years ago. With this
method, a three-dimensional photograph of the actual patient is taken and can
be seen on a large screen television by both the physician and perspective
breast augmentation patient at the same time. We then can place all of the
different implants that are available under that image and decide what size,
shape, fill ratio, and height to base width relationships will look best for
each patient. Silicone gel breast implants come basically into shapes either
round or shaped. They also come with either a textured or smooth surface. In my
mind, there are advantages and disadvantages of every scenario and combination
of those choices. Most of the time a round smooth implant placed under the
muscle works very well for breast augmentation patients. It's then very simple
to just look at size and ratio projection to base width and select the perfect
implant for that patients shape and desire. Sometimes we would like to use a
textured surface implant. Here the advantages are that the textured surface
implants tend to migrate less in the pocket, as there is some frictional
resistance to motion. Another advantage of textured implants is that the
capsular contracture rate, especially when implants put above the muscle, is
less than for smooth wall implants. Shaped implants, because we do not want
them to turn in the pocket, are always textured. My planning method to optimize
the best implant for each patient is begun with a measurement of the base width
of the breast. We would then like to subtract about a centimeter and a half
total off of that number so as to have coverage of breast tissue over the
implant. We then will have a range of implants whose base width matches that
number. If we go larger than that number, which sometimes patients will want,
we as plastic surgeons know that these larger implants can have more problems
down the line. For instance, larger implants may migrate below the crease which
one has to lower at the time of surgery in order to get the implant in. When
these implants migrate below the natural crease, they can create a second
crease in what we call a "double bubble". Large implants can also;
because of the pressure they put on the overlying breast tissue, thin that
tissue out such that there is less overlying breast tissue over the implant as
time passes. After we have the base width, our next decision needs to be what
is the ratio of the base width to the projection of the implant. Essentially,
there are usually four choices ranging from fairly flat which is called
low-profile, to progressively more height and less width with the same volume
of silicone gel, which is called ultrahigh profile. There are two profiles in
between which are the ones more commonly used and these are called moderate
profile and moderate profile plus. Common scenarios in which taller implants
would be desired may be in patients who want a larger look than their natural
base with would allow or have a fair amount of loose overlying skin that were
trying to hold up. For patients who want a more natural look, a moderate
profile or moderate profile plus shape is more desirable. There are also
anatomically shaped implants. Rather than being around these implants can
either be taller than they are wide or wider than they are tall. There are good
reasons in patients to use either. For instance, in the patient's with very
widely spaced breasts and a large breastbone, a shaped implant that's wider
than it is tall can help hide that a little bit. Another example of the patient
in who a shaped implant would be best, is that patient with laxity after
childbirth or weight loss. When the nipple is just at the level of the
inframammary crease, we can sometimes get away with a tall implant that is
anatomically shaped such that the nipple when is it at the lower two thirds of
the breast mound created by the implant still looks good and natural and may
obviate the need for a breast lift. By spending some time, long before the
operation takes place, using the Vectra® 3-D imaging method, we can decide what
type, shape, and ratio of width to height would best serve the patient's needs.
We can then avoid what is sometimes done which is the placement of sizers at
the time of surgery. These sizers, in my opinion, have a few negative
implications. One is that there is a cost inherent in using them and usually
multiple ones are needed to make a decision as to which implant would look
best. I also believe that placing sizers in and out of the breast pocket can be
traumatic to that pocket and can cause bleeding. For me, the state-of-the-art
in today's breast augmentation is to decide long before the operation exactly
which implant would look best using computer animation. A new wrinkle into the
choice of breast implants is that breast implants now come with silicone gel
that is filled to a higher volume in the shell where it is placed. This will
allow for a round smooth implant, for instance to collapse less in the upright
position mimicking more of the look of the shaped implant. When patients show
me a photo of a very rounded upper part her breast, I would likely choose one
of these higher volumes implants such as the Natrelle Inspira® silicone gel
breast implant. Often times patients will present with breasts that are of
different sizes. One of the options to correct this is to use breast implants
of different sizes in order to best create symmetry. One of the newer methods
to help in symmetry creation is to do what we call a hybrid breast
augmentation. In the hybrid breast augmentation, the patient who has asymmetry
of the breast to begin can have matching silicone gel implants placed and the
overlying breast tissue can be made to look the same in volume and shape by
using fat grafting. In that way, no matter what the change in weight of the
patient is over time, the breast is more likely to have the same or similar
size. When it comes to symmetry, I like to tell our patients that they should
consider their breasts to be sisters that live across the railroad tracks from
each other rather than twins. With proper preoperative planning and flawless
execution of breast augmentation, this can be one of the most satisfying
aesthetic plastic surgery outcomes for both patients and physicians.