I did what other reviewers recommended and I sized up. I usually wear a 36C or D, and I bought the 38D. It fit great, so I'm glad I got the bigger size. I don't think there's any way my usual size would fit me in this style. That being said, it's a super comfy bra. I have never had a wireless bra (that wasn't a sports bra) and I don't know how I lived without one. This is so comfy, and still gives me nice lift and coverage. Just remember to size up!