First, find your bust size by measuring around the fullest part of the chest while wearing a bra with little to no extra padding. If you don't have a tape measure, use a string and measure it against a ruler. Find your measurement on the size chart to determine your ideal UA sports bra size.
Standing straight up with an unpadded bra on, measure closely around the chest just under your arms, right above the bust. If your result is a fraction, round to the nearest whole number. (ex. 33.7" rounded to the nearest whole number, your band measurement is 34")
While wearing a non-padded bra, keep the tape parallel & measure at the fullest part of your bust. Round this measurement UP the nearest WHOLE number. Subtract BAND size from BUST size to find your CUP size. EX. 32” - 28”