30G/32F - What CC would I need to double my current size/volume? (Photos)

Thank you for your photographs. To give you the most accurate answer would require an examination of your breast dimensions. However, from your photographs, it appears that a 350 cc up to a 450 cc implant would likely double the volume of your breast. You could potentially do a water displacement evaluation at home by seeing approximately how much volume your breasts displace when placed underwater to give you a general idea of approximately how much volume you would require. Have a detailed discussion and consultation with your plastic surgeon about your wishes. Best wishes.

Thank you for posting your question here!My answer will be based on the limited information and pictures provided , for a detailed and bespoke plan please consult with your plastic surgeon
From the pictures provided it looks like you already have a lot of volume , you just lack the upper pole fullness. You already have stretch marks in your upper pole. I would encourage you to not think in terms of ccs or cupsizes, your surgeon will likely size your implant based on your breast width and ultimately your goals but going bigger than the recommended size will only give you issues in the future, if a lift is needed then considering a augmentation mastopexy is an option. where you place the implant matters too , big implants above the muscle with a skin that is already stretched without a supporting scaffold will just exacerbate the skin stretch and droop. I hope this helps, best of luck!