Ideally, how much narrower should your implant be than your natural breast width diameter? (photo)

Excellent question. In cases like yours, I like the implant to be just a little smaller than base width. If the patient wants a larger size than their base width, I change the projection of the implant. I use mostly moderate plus implants and occasionally high profile implants. Both look natural and the patients have been really happy. Talk it over with your board certified plastic surgeon and have a good plan prior to your surgery.Good luck!

Cup sizes are not standard across bra makers, and implant sizing is NOT based on height, weight, BMI, or capsize.  This is something you will need to do IN PERSON with an experienced surgeon to determine what works well for you, and to get advice about if what you like is possible and what to expect with regards to results.  Be sure to discuss your goals and concerns with your board certified plastic surgeon and consider the pros and the cons. Be certain your surgeon is properly certified.  I've attached a link where you can start your search.  

I normally size one cm down from measurement to implant size, however, I adjust this based on the characteristics of the patient’s anatomy.  Based on your photographs and the measurement you have given, I do not think there will be a problem with fit with the 335, if this implant has also been recommended by the surgeon who saw you in consultation.  The result would be expected to be very natural.
Best of luck to you with your surgery!

Nothing is more reassuring, than hearing from a RealSelf user who is thinking in terms of diameter rather than "cc." Patients often think in terms of cup size when considering augmentation. Unfortunately, devices are sized in terms of milliliters (cc) of volume. This can lead to some confusion when sizing. Additionally, it is important to remember that cup size itself is not standardized with variations from one manufacturer to another. Unfortunately, as many women can attest their cup size in an industry leader such as VS is not necessarily transferable to another brand.
Another point which is often under appreciated is that of anatomy and starting point. Any implant will add volume to the volume which is already present. The implant is additive. A particular volume will not necessarily confer the same cup size to different patients (often times it will not even confer the same cup size to different breasts in the same individual...remember they are "sisters" not "twins"). 
A general rule of thumb is that 125cc can represent somewhere between 1/2 to a full cup size increase. Smaller volume differentials (25-50cc) are typically less consequential representing a volume change of less than a shot glass. However, I have found these numbers, at least anecdotally, to be of little help. Patients often present with notions/goals which do not correlate with these sorts of sterile volumetric assessments.
When sizing patients, there are a number of useful tools including:
-3D imaging (has the added benefit of offering a volumetric analysis of the pre-operative breast)
-Breast sizers (rice bags)
-Goal photos
I also recommend that patients commit to a particular look rather than a cup size. Once a patient settles on a look that pleases them the overall cup size increase becomes less relevant.
With regards to your particular question, when considering 410 form stable shaped gels, the patient should aim to match or slightly exceed their planned pocket dimensions to ensure a snug fit. Undersizing can lead to malrotation. I tend to favor round gels for augmentation as I do not feel that the upper pole fill adds much in the setting of a patient with native breast tissue (as opposed to post-mastectomy patients with no native breast tissue). When using a round gel staying within 1 cm +/- of your measured with is advisable (with a preference towards "-" so as to avoid the dreaded lateral show and "fake" look).
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

Ideally 1 cm smaller than your base width.  That being said, an implant will usually fit right up to or even very slightly exceeding the base width if you prefer a fuller size, without folding inside the pocket (which leads to premature failure of the implant and can cause shape deformuties).

The breast width diameter in my opinion is one of the key determinants in selection volume and profile of the implant.  However it also depends upon the patient's goals.  I usually prefer to use an implant a bit wider than the breast diameter.

Thank you for the question.  There are no hard and fast rules when it comes to diameter of breast implant versus diameter of breast (band width). In other words, these measurements are useful but are only one of the many factors come into play when it comes to selection of appropriate breast implant size/profile.
You are correct however: every patient undergoing breast augmentation surgery should understand that their anatomic starting point will limit the outcome of breast augmentation surgery. The use of a larger breast implant (than what is safely "allowed" by the patient's anatomy) can be problematic;  potential problems include breast implant displacement/malpostion issues ( such as bottoming out, lateral displacement, symmastia...)  and/or significant breast implant rippling/palpability.
Other factors involved include surgeon dependent factors: for example, careful breast implant pocket dissection and careful selection of breast implant size/profile.  Remember (when it comes to breast implant pocket dissection and achievement of ideal breast implant cleavage) that each nipple/areola complex must be centered on each breast mound.
Ultimately, careful selection of plastic surgeon and careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
***Given that your surgery is coming up soon, I would suggest that you spend additional time communicating your goals/concerns directly with your plastic surgeon, preferably prior to the date of surgery.
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.
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. For example, I have found that the use of know words such as “natural” or "C or D 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.
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, after the use of temporary intraoperative sizers.
I hope this (and the attached link/video, dedicated to breast augmentation surgery sizing concerns) helps. Best wishes for an outcome that you will be very pleased with.

Thanks for your question. The ideal implant, is the one that fit perfect with your breast diameter and in that diameter you have a wide range of volume that you can choose. I really find that is a really small volume that was suggest. You will be amble to get bigger implant with that diameter of  13 cm. Almost all my patient are in your profile type, skinny with small amount of breast tissue and skin. If you want my personal advice i will happy to give it to you in consultation. 

Best wish
Dr Stephanie Olivier MD, FRCSC

Hello. Thank you for your inquiry.

It is important to have an in-person assessment regarding your concerns as it is difficult to determine virtually.
There are many different factors that go into choosing a breast implant size which will correspond with your body dimensions while concurrently achieving your aesthetic results. Some of these factors are: Implant size (CC's), Implant profile (Low, Moderate, High), Placement of the implant (Subglandular vs. Dual Plane) etc. We utilize smooth round cohesive silicone gel 'gummy bear' implants for the best results.
During a consultation your aesthetic goals are heard and taken into account with the measurements of your breasts and the integrity of your tissue, as well as level of ptosis (sag). From here we collectively can find your 'perfect fit'. You are able to try out sizers and different implants in our office such that you can get an idea of what size you would be post-operation. We also offer Crisalix 3D plastic surgery virtual simulator during our in-person and virtual consultations to preview potential results. After your consultation, you will receive your very own implant sizers to take home with you (at a small cost) whether or not you decide to go forward with your procedure.
I usually recommend that my patients stop smoking, take vitamin C daily, and avoid aspirin/ibuprofen and vitamin E 3 weeks prior to surgery. I specialize in the 24-hour Recovery method which minimizes trauma to the breast and decreases pain post-operatively.
We encourage you to look at our website and Instagram (drkaraplasticsurgery) for lots of before and after pictures!
Please note that this response does not substitute patient-doctor relationship. We welcome any and all patients seeking advice to come in for a complimentary consultation available for limited time only.
During the COVID-19, we are offering complimentary online consultations as well as in-office consultation with social distancing and masks. Procedure done in-hospital private surgical facility while taking covid-19 precautions. We utilize UV-light to clean the air of viruses and bacteria during our consultations and surgery.
We invite you to come in to discuss your options more thoroughly. Please send us an email at info@drkaraplasticsurgery.com with the subject line: "Attention Meagan" and we will be happy to coordinate your appointment!

M.Kara,MD,FRCSC (27+ years experience) - Specializing in 24 hour recovery/ out to dinner breast augmentation in-hospital private surgical facility for your added safety and peace of mind

Not a fan of cohesives myself. The diameter is most important. I do not understand your 'narrow enough to fit' comment. The difference in cleavage is not 0.5 cm but 1.0 cm , which is twice, since you are putting in two implants. In my opinion the larger implant would give the most natural look since it mimics your natural cleavage/diameter the best. Try them on in a bra and put a T-shirt over it. It's probably better than any computer program.All the best,Talmage Raine MD