What size would a 400 gram breast reduction bring me to if I'm a 32H?

Breast reduction for treatment of back pain and other symptoms of macromastia is one of the most satisfying procedures I do for me personally and my patients. The insurances requirements, include how long you have been symptomatic, what treatment you have had as well as requirements for quantity of grams of tissue removal,  and vary from one insurance company to another.  Some insurance companies are now writing exclusions for breast reductions out of their policies. My patient coordinator has been working with insurance companies for 20 years working to get my patients precertified for surgery.  I suggest you consult a board certified plastic surgeon with an extensive experience with breast reduction surgery. Best of luck.

Thank you for the question and congratulations on your decision to proceed with breast reduction surgery; this operation tends to be one of the most patient pleasing operations we perform.
There is no direct/reliable correlation between the amount of tissue removed and the ultimate cup size that a patient will wear after breast reduction surgery.

Before undergoing the breast reduction procedure it will be very important to communicate your size goals with your surgeon (who you should choose very carefully). Most patients wish to achieve enough of a reduction to help with their symptoms while remaining proportionate with the remainder of their torso.
With the goal of improving communication with my patients I find the use of photographs of “goal” pictures (and breasts that are too big or too small) very helpful. For example, I have found that the use of words such as “natural” or “B or C cup” means different things to different people and therefore prove unhelpful. Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate. Once you have communicated your goals carefully, your plastic surgeon will be able to provide you with an estimation of how much tissue will need to be removed, in order to achieve your desired outcome.
Best wishes with your breast reduction procedure; hopefully you will be very pleased with the outcome of the procedure performed.