This is specific to the Lounge Bra, NOT the sports bra. Warning to anyone who is looking at the Perfect Lounge Bra, the size chart is totally inaccurate, and Shefit customer service will recommend you size UP. Sizing UP may give you adequate bust size, but could end up being HUGE in the band size (under the bust). The cup sizes for the Lounge bra are adequate for a B or C cup, and nothing bigger. The under-bust runs huge. SheFit staff recommended I get the Luxe - I take a Medium in the sports bra. I provided my measurments, and asked if they were SURE I'd take something that big, since I was quite small around? The Luxe was WAY too big - I was "flopping out" of it. I would estimate it was about a 38 or 40 B/C. So I exchanged for a Medium - closer around, although still large in the under-bust - about a 34/36. OTOH, the cup size was way too small - again, a B/C cup size. There is also very little support - the Lounge Bra is kind of like wearing a tube top - remember those from the 1970s? Although staff assured me they have great support. After shipping back 2 bras (remember, the customer pays shipping back), I gave up and cut my losses. So - in summary - if you are a B/C cup, these might work for you - but anything bigger, and forget it. Ignore the size chart - it is totally inaccurate. I haven't seen the Small size, but based on my experience with the Medium and Luxe, I'm going to guess it is a 32/34 B/C cup. Medium - more like 34/36, B/C cup, and Luxe - 36/38 B/C cup... If you are bigger in cup size - don't waste your money.