Will 275cc give me a full B cup? (Photo)

The implant size you are considering should give you a nice result. Many surgeons have sample implants you can "try on" to give you an idea of how you will look after surgery. I encourage you to discuss your concerns with your surgeon so that you can feel comfortable and confident as you prepare for surgery.

A board certified plastic surgeon will be able to guide you to the correct size implant. Based upon measurements of your chest wall and breast imprint width should make this process easy. None of the modalities to approximate final results from breast implants are 100% accurate; they merely facilitate the patient and the board certified PS concurring on the size and type of breast implant which will come the closest to reaching the patient's goal.
During an office visit, my patients prefer to try on implant sizers under garments they typically wear (workout tops, bikini, tight sweater, low cut dress) to determine if they fit as expected and help allay some of their trepidation associated with this decision. I would recommend that you go with the size that boosts your self-esteem, and fits your anatomy. A very general estimate is that one cup size is 150 to 200 cc of volume, but realize that no direct correlation exists between the two. It's unlikely that you will notice a difference in increments less than 100.