I am a large A cup with typically a 34-36 band and I purchased size S. They're almost exactly like the version sold by Free People, however the material is softer and these come with hefty cups. I took the cups out because they were causing the whole bra to ride up in spite of strap adjustments. Taking the cups out fixed that problem. The band is generous so if you're worried about sizing, I'd size down. I could probably use an XS in these to keep them in place. Overall, I really like them. They would be five stars if the fit was a bit more spot on.