Why Does Breast Augmentation Also Increase Band Size?

That is an excellent question and one I wonder about myself. You would expect only the cup to increase with breast implants. There is no definitive answer and probably assocated with edema or tissue creep.

You are correct, only the cup size changes with an augmentation and not the band size if you are at the same weight. The differences may be attributed to a different bra type or manufacturer, or which clasp is used to fasten the bra strap

The problem with the cup size system is that it is not based on a pure volume measurement of the breast, so predicting the changes with augmentation can be tricky. In theory it should not change the band size. However, sometimes the bottom fold of the breast is lowered a little bit with augmentation so the band will be on a different level.

You are correct in noting that breast augmentation only increases the cup size. The number on a bra is the circumference of the chest wall. An increase in this number typically indicates an increase in weight, not breast size.

The circumference of the back does not change. However the fitter of the bra may place a person in a different cups or band size depending on how the bra fits.

Quite simply it is a geometric increase in 3 dimensions. If you increase the projection or the anterior surface of a cylinder than the circumference of that cylinder increases its size also. Assume the chest cavity is that cylinder adding to it will increase the "band" width. I hope that clears it for you. Regards Dr. B from MIAMI 

I agree with the answers of Dr. Baxter and Dr. Whitt. A properly fitted breast implant only increases the cup size in the same chest circumference (band size). It acts like a pillow behind the breast (but not like an external cup filler) and has nothing to do with chest circumference. However, adjusting the crease level or filling out the sides of the width of the breast can make bras fit differently and sometimes a larger band size will seem to fit better. 

I use the patient's existing chest circumference as a reference for what the cup size will increase to in that bra size but after two weeks of healing, I tell a patient to wear whatever she feels fits and looks good (or nothing) and not worry about what it says on the tag of the bra. 

If you want to see how this works, go to a bra store and look at bras with formed cups and look at C-cups in 32, 34, 36, and 38 around. They will not be the same but for a properly fitted implant, the woman's band size will stay the same and the cup size within that band size is what goes up. Look at your band size and then look at A, B, and C cups. Again, this isn't helpful when used as an external measure with a filler to judge the implant size or the effect of a given implant volume. Get the procedure done properly and choose the forward projection of the implant to increase volume but wear whatever you feel fits and looks good. 

You are correct.  Augmentation changes the cup size but should not alter the Chest size (34, 36, etc.).