A 28DD is small. VERY small. Its sister sizes are 30C and 32A. A 42DD is massive. The cup is relative to the band size.

$ 20.50 · 4.9 (98) · In stock

28E / 28DD White Bralette,yoga Bra,wireless Sports Bra,28 Size Bra,size 28 Bra Band,adjustable Bralette,supportive Bralette,small Band Bra - Canada

What bra size should I try next, I am currently a 42b but the cup wrinkles and is cutting into my sides? - Quora

Sister size, Bustyresources Wiki

Sister Sizes: The Bra Secret Every Person Should Know – Sister Sizes & Equivalent Bra Size Chart – ThirdLove

Sister Sizing De-Mystified! – Playful Promises USA

Understanding Bra Sister Sizes

I'm lost! Am I a 32G/GG or a 34F? : r/ABraThatFits

Bra Sister Sizes + Sister Size Chart

How Bra Sizes Work: A Full Guide

Is 12c bra size big? - Quora

What is the difference between B, C, and D bra sizes? - Quora

Bras: What is Sister Sizing? Bra Sizing Explained by Kimmay

Sister Sizes: The Bra Secret Every Person Should Know – Sister Sizes & Equivalent Bra Size Chart – ThirdLove