What bra size is bigger 34 D or 34 DD?

Answer 1

The 34DD would be bigger by one cup size, which equals one inch.

Someone whose ribcage equals 34 inches and their bust equals 39 inches would wear a 34DD, since there is a 4 inch difference.

Someone whose ribcage equals 34 inches and their bust equals 38 inches would wear a 34D, since there is a 5 inch difference.

Both of these sizes would be on someone with proportionally small breasts since there is only a 4 or 5 inch difference, and have a good chance of having a shallow shape. A shallow shape means the breast tissue is spread out over a large area, usually up to the collarbone, and would not project much. Shallow shapes usually have wide roots as well, and would need Bras with wide wires.