Even better, computer enhancement, if it is available, but do not rely on it. Call your implant company for a brochure on the width height and projection of each implant. This does not substitute for an experienced surgeon, it's just an aid to give you an idea. For example, if you like 300cc of rice, you'll need 330 to 345cc implants. Also, projection after surgery is less than what you see in the bra.
Implants tend to be rounder and fuller.
This is particularly true with sub muscular placement. However, anatomicals do have more projection than rounds. The measurement that I use is to measure the distance from your desired cleavage point to your nipple. For example if that measurement was 8.5cm. than I would use the 300cc. If It were 9.5cm. than I would use a 325cc.