Why breast implant manufacturers do not indicate cup sizes?
Cup size is one of the common indicators for describing breast size or for choosing the bra size that is right for you. However, cup size differs according to the under-bust or thorax measurement (the circumference of the thorax measured at the inframammary fold). The larger the under-bust size is, the larger the cup size will be. Moreover, as you may have noticed from personal experience, cup sizes differ between brands – a C cup of one manufacturer may fit you better than that of another one.
This hints at the problem: cup sizes are relative and, what’s more problematic, are not standardized. Therefore, cup size is not helpful as an indicator for defining breast implant size! That is why breast implant manufacturers initially chose volume (cc / ml) as measuring unit for implants.
Today, additional measurements help surgeons define the best fit for their patients: In implant catalogues, you usually find measurements for the base width, base height, and projection. (The base of the implant is its back, placed on the thorax; the projection is the distance between the back of the implant and its maximal point of curvature.)
A trick to find out what breast implant size suits you best
If you are considering having breast augmentation, a first step to have a feel of the size you want can be to fill some pouches with water or rice and put them into your sports bra. Add or reduce until you have found the size that goes well with your body (and your wardrobe!). Then spill the content into a beaker and measure the volume. This may give you an idea and provide you with a starting point before consulting with your surgeon.