The cup size of a bra is determined by the difference - Band to Bust – BRABAR

The cup size of a bra is determined by the difference between the rib cage measurement and the overbust measurement, so a 28DD size bra is 28 inch rib cage and 34 inch overbust measurement because 28 inch (rib cage) + 6 inch (difference) = 34 (overbust). Therefore, the cup size in this case would be DD. A 32D bra size.

Bra Fitting 101 – Lace of Love

Bra Fitting 101 – Lace of Love

Bra size - Wikipedia

Comparing Cup Sizes: A vs. B vs. C vs. D Cup Size

Are Band Size and Cup Size the Same

How to measure your bra size

The cup size of a bra is determined by the difference - Band to Bust – BRABAR

Bra Cup Size Comparison

Sports Bras: Sizing & Measuring