Aesthetically Ideal Areola Size, How to Calculate

There is no ideal size!  Plastic surgery is an art and science.  This falls under art.  This is a personal choice.  If you want a very large or very small areola then that is what you want.  Your surgeon can share their experience and their preference.  At the end of the day it is your choice.  Find photos of what you like.  Share that with your plastic surgeon.  That is far more valuable than any calculation.  Ideally your plastic surgeon's goal is to make your vision come true, not their own.

There is tremendous variation in areola size,as there is in breast size and shape

So the areola size is really a personal choice

It is possible to reconstruct a nipple areola complex fairly accurately in the reconstruction patient,however in the augmentation ,breast reduction and breast lift patient  it is more unpredictable as stretching occurs to varying degrees after surgery

Areolar size will also vary depending on the amount of stretch placed on the areola at the time of measurement during surgery ,As you mentioned the areola is a contractile organ and size will vary with temperature and stimulation